That is largely because the AI part of the buying process is not done, yet. And also because we play by forum now.
In the final game, you will offer a price, the NPC will say yes or no, you can offer a lower price, etc.
Every time you offer a too high price, customer loyalty will drop slightly. Every time they buy, it will rise slightly. So you can play games like offering a few simple things cheaply at first to get them to do that big buy, etc.