Baldur's Gate

There is a table with the values in the manual. If you didn't get a paper manual then there should be one on the disc, if there isn't you can download one from sorcerers.net.

It varies between 100 and 500 gold. It's lowest around Reputation 10 or so. Check the manual or Save and Reload.

or...

If you're too lazy to do either, here's a somewhat complete guide straight from the manual i am looking up right now as i speak.

for some reason, you won't get any more points if you have 18 or more.

17 reputation points - 500 gold for one more
16 - 400
15 - 300
14 - 300
12 - 200
11 - 100
10 - 100
9 - 100
8 - 100
7 - 100
6 - 200
5 - 200
4 - 200
3 - 300
2 - 400
1 - 500

hope this helps.