Board Thread:Game Discussion/@comment-27109924-20151125080816/@comment-26715739-20151126155935

For me (but judging by other people's comments, not for others) it's always given me the full discount on unlock - ie if there's a sale I get the sale price. This is what happened for me with the Spada when it was on sale a few weeks ago.

So I'd recommend you do as RomGuyony suggests and cloud save before you give it a go. That way you only lose the time for that last race if there's a problem.