I'm still playing my Dark Side four paladin, mage, cleric-thief party and I'm finishing up the last unfinished quest (the archeological idol one) outside of BG city. The DS quests are completed (again, outside of BG city--not sure if there are any further DS quests inside the city), and the Durlag's quests are finished also. I have played it squeaky clean--no thieving beyond taking stuff from evildoers (eg, picking locks in the bandit camp) who have tried to kill me. I now have 305,000 simoleans! (Btw, didn't certain orders of knights amass unbelievable wealth during the Crusades?) Got the rep up to 20 as the first order of business and they got the items they needed very earlier on. Plus, they're all meleers so I never have to buy arrows, etc. Anyway, I sell most of the stuff I come across and never have to buy much of anything. I certainly won't have any trouble buying my reputation back!

I know you can rake in over 275,000 gp in straight BG1 if you rob everyone....I'd estimate that in ToSC, you can get at least 400,000, but I don't know for sure, 'cause the last time I played it all the way through I didn't rob folks, as I was playing a Paladin. Once you've bought the expensive goodies like the Shadow Armor and the Archmagi Robe, money becomes pretty worthless anyway (unless you want to recharge the Wand of Polymorphing, which I never used).

Alone, Durlag's Tower gives you a billion GP with all the nice bolts and arrows.

There is a bug that some people have encountered in Durlag's that if they leave the dungeon at a certain level (not sure which one) they can't get back in (again, not sure which level this happens at when trying to get back in). So having read those accounts so frequently I only go back out to sell after doing the four upper floors, basement, and the level with the warders. Beyond that I just gather up whatever I can manage to carry.