Dallan: Those were the grips you bid on? They are handsome! What was the final price? I'd guess probably around $50.
I bid on a set of grips for my Smith some time ago. I really wanted them, but they went for way over what I was willing to pay.
I finally got a set that I like almost as well, for less than what the original set went for, and I like them buuuut.....
You have to ask yourself what it's worth to surprise your dad? A "fair price" will be determined by who else has the big eye for whatever you are bidding on, and how bad he wants it.
One guy paid about $20 for three poorly-copied pages showing how to make a gillie suit.
I got mine for $2.75, where the emotion wasn't quite as high.
Set your limit, and stick to it. If you miss 3 or 4, you know you need to raise it a bit.