
You should have hundreds of thousands gold right now (less if you play lonewolf, but you need less money too, so.), and no more books/runes/frames to buy (=to steal), so you can spend all this gold on gear. But if you had thievery until now, you won't need it anymore.

Then bartering should start to be useful. In Arx, legendary items cost usually something between 1500 golds without any discount. And every character can steal, and you still need nothing to do so. With thievery, you need nothing but a hidden spot, which is very important during the first act, when you don't have much money but so much books to buy. And the better, for bartering being used, you have to sell something first (or having gold). Even in selling and buying at the same time with one merchant, you would never be able to spend that much at this level (you don't have the gold, and the merchant don't have stuff so much expansive). Or you would have to sell for more 20000 gold (something like that) to have a 800 value on the increased sellings. If you go on another one (you'll never buy/sell so much on only one merchant at level 1), you need to double this, since there will be 2 theft, so 126 books.

And of course, all these books on the same merchant. You would have to buy 63 (!) books to start to compete against thievery (810/13). So basically, you have a discount of 13 gold on every book. 324 for every book (120 value in thievery mode). Most expansive stuff at this level are books. You have 4% discount at level 1 on bartering. The gold value is a special value only for thievery (something like x2,7 the usual values, so basically you can steal in fact something like 810 gold value). At level 1, you can steal for a value of 300 gold with thievery. With 1 point in thievery you can steal far more gold value than what you can spare with 1 point in bartering, and it's scaling all along the game. :p Thievery is much better than bartering until very, very late in the game (and so much better in the end, since in the end you'll never need bartering if you had thievery before that).
