Well, here is what I think.
From what I can gather here, it seems as if this Melo deal is basically a 1 year loan for 1.5 million, where in essence he has the opportunity to double his salary as a one off situation.
With those salaries in question coming off the books, with the likely exception being Del Piero possibly being brought back for 1 year, what this move does is it gives Juve the financial flexibilty salary wise to take on either 1 large salary this year, or 2 additional good salaries, all the while being able to acquire an additional player or players that will fit the salary budget that they have in place. But the key here is what it will do NEXT year.
Taking into account the revenue streams being brought from ticket sales, and luxury suites, added into the fact that most of those salaries are going to be completely off the books, this could put Juventus in a very healthy situation in regards to player salaries.
Now, I know that some people are going to say "Why didn't they just keep Melo this year?". The reason is because I think they have set themselves a certain amount for salaries this year, and his salary, including any potential new signings, taking into account that Conte doesn't see him as a starter, would have been too high for them this year.