The thing with Melo, was a price and mentality thing.
1) Nobody except Gala was interested in a bat$#@! mentally insane midfielder
2) We absolutely wanted to sell, and Gala knew it, and knew there was no competition and Melo wanted to stay in a place he felt home. So they tried and partially succeeded in undercutting.
The thing with Sneijder, is different.
1) The player wants a raise and isnt getting it, and wants out.
2) Apart from juve, no team close to our reputation or finances has shown interest
3) Sneijder can threaten to have his contract rescinded because of outstanding payments due.
Gala fans might want ask Athletic Bilbao and Manchester City how its like to have Marotta undercut you for a player that wants out and has no other suitors