Yes and No.
Last year with the single Merc 350 I was aware but the prices didn't really effect what I did. This year with the new boat and twin 5.0 Volvos I don't think I'll take less trips, but I'll be far more carefull of exactly how far down I push the throttles. Filled up the new boat for the first time last Saturday $500.
For those of you who are concerned, check out
http://www.boattest.com, in their reviews they usually give performance data which shows the most efficient RPM's to run each boat in.