check out www.executivelounges.com - Globeground/Servisair have a couple of lounges at AMS - one in Schengen, the other outside.

It's quoting GBP16 for three hours (so approx USD30). You would go up the wall if you spent 12hrs in one of those places, but this may do the trick.

I'm not sure how strict they are on the 3hr rule, and I don't know if you can buy at the door, but check it out.