To the best of my knowledge, the final price would come down to the evaluation of intangible assets (brand, good wills, future cashflows, etc).
If we approach Inter's intangible assets from market perspective, then Milan is a good reference (1.2 b).
If we approach from, say, risk or cost perspective, then we have to think about whether paying 1.2b worth it or not, considering other possible substitutes. This is where thing might get dark. With 1.2b, you may have a chance to buy other clubs with more future achievements. In my opinion, if Inzaghi does not win Scudetto, or does not make Inter a clear favorite in the next couple of months, Inter price would go down quite a bit.
The whole situation can be even worse, if the evaluation of Inter's assets is based on some steady stream of income cashflows, then things like sponsors, merchandise, etc would be bigger contributing factors. These things, I am afraid, will tell evaluators that even though we are winning, Inter is not a very attractive.
.h. or breme you guys may have more knowledge about different evaluation approaches?