The Runlondon website has this to say on whether Nike makes money:
"No. RunLondon is a non-profit event. Fees from registration are invested in the events, plus Nike invests additional money to ensure the quality of training runs, race packs and the events themselves"
Whether you believe them or not is up to you.
I did the Paris half marathon this year, which cost around £20 as I remember. It was a great event, but certainly not as well organised as last year's Nike 10k, no warm up, and only a cheap T-shirt.
Last year's Nike 10k was my first ever race, and in a year I can honestly say that I haven't done a race since which was as inclusive, as well organised or as much fun (and certainly nothing with as swanky a piece of free kit!).
If you think it's too expensive then don't do it, but you'll miss out on a really fun race. Hell, I'm in!