SanDisk, Kingston and Transcend CAN all have problems with counterfeits -- I am NOT saying they are the only ones to have it, or that you are going to get a counterfeit, but they are big names so they are more likely targets -- so watch where you buy from.
I recommend ADATA, I bought mine from NewEgg.com I'm sure you can find a reputable low-cost computer dealer in your country.
From what I've seen:
- In terms of price, ADATA is typically one of the cheapest.
- In terms of speed, from what I've seen they tend to have fast Read Speeds and low Random Access times (both what you want to look for).
- In terms of Class, their Class 6s are usually as cheap as others Class 4s (Class is ONLY write speed, but faster write usually relates to faster read speeds).