If I'm not mistaken, shop prices are much higher now than they used to be. Can anyone confirm this? This is probably because of rfe 2809. What's even weirder: prices in the black market went UP by a fair margin after I became head of the thieves guild.
The RFE was meant to be a measure against sell-robbing. But so far, I see no difference in the prices of items you sell to them. The prices they ask are higher, but that does not have any effect on sell-robbing. If would be the case, this feature made it more attractive than ever to kill shopkeeps (and less attractive to buy anything from them).
edit: it even seems that the prices they offer are higher than they used to be!