Prestige is a leveling system; the more prestige you have, the higher level you will be, and the more things you can buy. The highest level you can be is 1,000. Like money, prestiege has icons for how much you earn. The most prestige you can get off an item is the Stradivarius Violin, with 1039, or with the Double Prestige promotion, 2078.
A prestige chart, featuring how much prestige you need to get to the next level (currently up to 100) can be found here.