Right now it is closer to $1.5 lower then stamp. I have noticed that it is generally somewhat lower, but I wouldn't say it is 1-2% lower.

I would tend to agree with the above argument that since btc-e does not complete any KYC verifications it is going to attract people who value their privacy. Since it is the sale of bitcoin that is going to trigger potential taxes, people are going to want to use them to sell bitcoin more often then they are going to want to use them to buy bitcoin (when taxes are not applicable)