Transfer fees were obviously a lot different in 2008 and 2010.
Both of those guys are also older than Gigi, obviously never a possibility to be in line as his successor, and Manninger was even the 3rd string keeper for awhile. Neither was purchased by Juventus with the idea that they were buying one of the league's best.
I don't really get the transfer fee or salary comparisons, Pitbull. Buffon is 40 in 3 days, Szczęsny is basically entering his prime years, arrived after a year where he was right at the top of his craft in Serie A, and at this point everybody has indicated that the plan is for him to be Gigi's successor -- including Gigi, Szczęsny, and management. That writing has always been on the wall.
It'll be different around the club and in the locker room once Buffon is gone, but there's no real reason to think Wojciech will suddenly and randomly go off the rails. He's still going to have a better defense and team in front of him than he had at Roma, and if he plays like he did last year, and like he has this year, the club has its new #1.
If for some strange reason he doesn't turn out to be the guy they want to stick with, 12.2M + 3.1M in Bonuses is amortized over 4 years. So any outgoing transfer fee easily covers any potential loss.... it's really a no-lose situation, as far as I can tell. Even if he bangs all the WAGs of Beppe and Co. during the second half of the season, and has to go, they'd still only have to get around 11.5M this summer to clean up the books.
Another successful market opportunity for the braintrust!