Sony sold over 5 million units of GT 5 prologue. When the real GT 5 released the production costs were already paid and maybe the game already made profit with the Prologue. Besides the marketing campaign and the usual split of the revenue for each sale the game made pure profit to Sony. Or not? 

Yes the game was pure profit. However the system (ps3) ate all of that and more ( like billions more). So in reality its wasnt profit at all for sony.

Yeah it was,  and much needed revenue for Sony at the time.  

I believe GT Sport is the prologue of this gen and will basically pay off the entire costs of GT7 and then some.  Because it's not named prologue and is being fledged as a full game I think it'll sell more than a prologue would have.  In reality it's a glorified prologue but Sony were smart to do it this way. 

Irrelevant. Profits and losses of the past don't matter to any company. The current and future is what's important.

Yes its an interesting strategy sony used with the GT series. they give you a small taste of the gsme and call it prologue, concept or sport (in the current case) and use the money made from that release to pay off the dev and marketing costs of the numbered release.

I think Konami did something similar with ground zeroes.