I purchased 3 contracts through GMAC. I can only speak about them, but there were four costs to the contract (I think most of the other companies have only three).
1) Negotiated contract price (# of points X price per point)
2) Maintenance fees (can be negotiated with the seller)
3) Closing costs (can be negotiated with the seller)
4) GMAC fee ($195 - can be negotiated with the seller - I don't think the other 3 sellers mentioned on the boards charge an additional fee)
For two contracts, I did not pay closing costs or the GMAC fee. For the 3rd contract, it was loaded, so I paid the $195 fee, but no closing costs. I paid the maintenance fees on all 3 contracts since I purchased them in the beginning of the year, and would have full use of the points.
In case you're wondering, all three contracts closed within 2.5 months (offer to being in Dis's system and able to make reservations).