Usually it from forcing people to pay 5k USD. Some people, and this may be a hard concept for some people. Are really poor and try to make a living off OTS. One of the greatest things about otland and the open tibia community was that if people could make something and make some money they could help themselves.
Then you get people that come in and want people to pay way more than they should for advancements. Now, there is nothing wrong with someone wanting to sell work they have done. That is how the world works. The problem is when you use an open source, free project, that is a critical part for ALL people trying to create a server and make it an outrageous price.
Of course that is all subjective. If I spend a month working on something I may feel its worth a lot more. That's still not the problem. The main problem is that this type of thing will essentially make it impossible for the average person that didn't have the privilege's of going to a school, or can't spend hours learning how to do the same thing, to create a server and make some money.
To sum it up you have a couple developers that monopolize open-tibia. Which is pathetic in a lot of peoples eyes. Even as someone who doesn't use open-tibia shit like me. They are too worried about making as much money as possible for the least amount of work and not worried about who they could be effecting.