Gust googled it (Mail) - apparently Man U got £15m for winning it last year. As you say, most of the PL earnings come from a percentage from live TV appearances and an equal pay-out of £33m that all clubs get.
They reckon with the new TV deals, the club who finish bottom in future will probably earn more than Man U did in total for finishing top in 2013! Again, it'll be interesting to see how much of that actually relates to the prize fund though...