probably because at this very moment, trez is stronger than huntelaar. Trez has CL experience, something money can't buy. It's clear that barca want to strengthen their squad for immediate success, they can't rebuild a new team around youngsters. They have the money and they buy themselves a full-grown, CL-ready squad. if trez retires in 2 seasons, so be it, they'll have the money to replace him again.
I still don't know if we're doing the right thing if we change trez for hunter... in any case, we should never ever sell trez before we haven't hunter's signature in the bag. And i'd never want a quagliarella or podolski or something. IF we do this, then f-ing get hunter!