A few dollars at most, and then only as the slightest reminder of where I've been. Souvenirs are too often shlocky, mass-produced bits of fluff that don't draw my attention even the slightest bit. When I was in the UK not too long ago I must have seen the same standee filled with Coats-of-Arms in about fifteen different shops. (And none of them had my name anyway. Peh!) I'm much more likely to purchase something if it is hand-made or otherwise unique in some way. The usual sovenir stuff is just... blegh.