It is prejudice when you buy something based upon it's price. If you have scientifically tested a given brand and found out that it really overclocks better than another, cheaper one, then it is ok. Even then, the right answer would be "Stay away from this or that brand" and not "Stay away from cheaper products." Such an answer has no value for someone who's trying to find out some specific information about what to buy. But otherwise the price shouldn't matter as long as you look at the entire specs, e.g.:
Type (DDR2 over DDR), capacity, CL, and frequency.
Another issue is how long the RAM might last, but given those numerous RAMs with lifetime warranties that's not much of an issue either.