I am currently looking at 32GB class 10 SDHC cards. The prices per brand are extremely varied.
For example:
What is the cause of the price difference?
This creates the perception in my mind that the Transcend card must be a piece of junk that I should not buy. Is this true? Or is it just a much better deal?
Are the differences just for pros? Something an amateur like me wouldn't notice, or does the difference mean the cheaper ones will die sooner?
Reliability, brand, exclusivity determine the price of memory card.
SanDisk, for example, has multiple series, usually with different colors. Blue ones are low end and not entirely reliable. Black ones are more durable, usually labelled 'Extreme' and red 'Ducati' edition which are modified extreme with additional durability and performance testing. The red ones are more expensive than the black ones, but I find them equally reliable (zero failures among 12 black and 4 red cards I own).
Lexar has a similar color-scheme with higher reliability for more premium lines. Lexar memory devices are all extremely reliable but they are, as you may notice, more expensive than competitors.
Then there are tons of other brands. Kingston for example as an excellent one and cheap because it does not the brand recognition of the big two. Now when it gets cheaper than that, reliability suffers. It is not that they won't work, but you'll get more and more corrupted photos (examples have been posted to this site by unlucky ones) or a card that simply stops working.
Your risk depends on your workflow and how important your photos are. For example, if you copy your images every day, you will lose at most one day of photos. Even a brand name card can fail, I've never experienced it, but if you search around, you'll find.
I never heard of Raw Steel, but it sounds like they have produced a premium product. How much it matters, I do not know. I've had both Lexar and Verbatim cards come out of the laundry without any negative impact.
SDHC cards get a class rating (6, 8, 10) which denotes how fast the card can transfer data, higher class cards will transfer data faster and for that reason cost more money. However the 3 cards you've linked to are all class 10.
The other difference between them is quality, cheaper cards are more likely to fail sooner in my experience. I've had a search around and I can't find any studies done on this, maybe someone else can. I've personally had issue's with a Transcend branded card very early in its life and since then I've only bought Kingston cards (and have yet to have an issue). Others will likely recommend other brands.
It's my understanding that flash memory is actually produced in very few places by very few companies and that the majority of brands that you find on cards haven't actually produced the flash memory itself, they simply buy it from the places that do and put their own branding on it. I suspect that some of the cheaper brands will buy the lower quality samples from factories!
I won't tell you to buy the most expensive card but neither will I tell you to by the cheapest either, I'm afraid you have to decide how much you feel is a reasonable price and shop around.
There are two basic types of flash memory: Single-level cell (SLC) and multi-level cell (MLC). By using multiple voltage levels to store information, MLC memory can pack more data into the same area of silicon, bringing price down. However, this improved density causes disadvantages when it comes to read/write speeds and write endurance. Therefore, lower-cost cards typically are MLC types, while higher-cost cards are SLC.
You should also be aware of the rather complex supply chain for these cards. In the flash fabrication department, Toshiba partners with SanDisk, Intel partners with Micron, and Infineon, Micron, Renesas, Samsung, and ST Microelectronics round out the major suppliers. Most of these companies also make the controllers for the memory, but there are even more companies that make their own controllers. See this 10-k filing by Lexar from way back in 2005:
[Excerpt 1] We compete with semiconductor companies that manufacture and sell flash memory chips or flash memory cards. These include Hynix, Infineon, Micron, Renesas, Samsung, SanDisk, ST Micro and Toshiba. Micron and Intel have recently formed a joint venture known as Intel Micron Flash Technologies. SanDisk and Toshiba jointly develop and manufacture both low-cost and high-performance flash memory through their Flash Vision joint venture.
[Excerpt 2] We also face significant competition from manufacturers or card assemblers and resellers that either resell flash cards purchased from others or assemble cards from controllers and flash memory chips purchased from companies such as Renesas, Samsung or Toshiba, into flash cards. These companies include Crucial, Dane-Elec, Delkin Devices, Feiya, Fuji, Hagiwara, Hama, Hewlett Packard, Data I/O, Infineon, Kingston, Kodak, M-Systems, Matsushita, Memorex, Memory Plus, Micron, PNY, PQI, Pretec, Ritek, Samsung, SanDisk, Silicon Storage Technology, SimpleTech, SMART Modular Technologies, Sony, TDK, Transcend, Viking InterWorks and many others.
[Excerpt 3] In addition, an increasing number of companies are manufacturing their own controllers, including Genesys, Hyperstone, Prolific, SanDisk, Sigmatel, Silicon Storage Technology, SMI, Solid State System, Sony and Zoran. Such companies either combine their controllers with flash memory from third parties to manufacture their own flash cards or sell their controllers to third parties who use them to assemble flash cards. Additionally, major semiconductor companies such as Infineon, Micron, Renesas, Samsung and Toshiba have also developed or are currently developing their own controllers that will likely compete with our controller and/or card sales.
Importantly, note that some manufacturers, including the Kingston brand praised in other answers to this question, doesn't manufacture any flash memory. They buy it from their competitors. The only value-add that Kingston offers is branding, packaging, testing, and controller firmware.
That said, I don't know which of those three links use which type of memory, or which Flash foundry, or which controller. I know that the SD card manufacturing industry is full of counterfeits, so be careful who you buy from (See this post from Bunnie Studios for an example of the counterfeiting in Kingston cards).
How important is your data? If you can risk some card failures, Transcend can offer a great value. My own searches show Transcend with a spotty record. Some cards are really good and some really mediocre. A professional photographer friend of mine uses nothing but Sandisk because they have a really low failure rate. I haven't heard of Raw Steel and doubt that they can offer that much more to offset double the price of the Sandisk.
In short, there is no good answer other than keeping up with feedback from the masses.
Many of the brand vendors don't produce their own flash cards. This combined with some rather nasty competition has lead to a lot of low quality components on the market from time to time. Even within a brand, I wouldn't expect quality to stay consistent even with the same technology and highly likely to change when there is a technology shift.
I've generally stayed with the lower priced bands that don't have significant complaints. For me, this meant Transcend.
Note, all flash drives have a limited life span and that life span is much shorter than most people expect. The life span is a factor of how many times each area of the code is written. If you are a very heavy user, you will see card failures. It should be part of the plan. I am not a very heavy user, which is why I haven't seen too many issues.
I would hope that the more expensive cards have been designed for an increased number of writes. You may be able to get this information online in the form of MTBF (mean time between failure) numbers. This topic has been much more important in the SSD arena where users are much more likely to hit these limits. And, while the numbers might trend with certain vendors, I've seen a fair amount of variability within similar product lines.
http://www.overclockers.com.au/wiki/Flash_Memory http://www.vampiric.us/articles/Hardware/CompactFlash/FlashMediaSpecifications.asp
