I'll give a quick example of 'silly prices' and their effects.
Currently, to buy 10 credits will cost about 2 to 2.4mil gc : to buy a Pouch of Gold in the voodoo market costs between 9 and 10.5 credits : but its best value is only 1mil gc, thats the most it can bring back. It's other purpose, to check a players purse size, is also rendered overly expensive, when considered as a cost in a raid, along with all the other over-priced voodoo required. Let's not forget, the purpose of a raid is to show a profit at the end of it!
Thats just one example of over-pricing, there are countless others. The high cost of buying credits amplifies that poor value.
So, when next the notion that we can be encouraged to attack more is raised, lets consider that it has to be a worthwhile exercise in the first place. Limiting the number of places which can buy and sell credits can only strangle a market : there is little incentive for radical price movements, the herd follows the best price it can get : that's not necessarily the best price for the game and its needs.