It seems to me that the economics of race photos has similarities with the economics of race events themselves. The bigger the event, the higher the price that the provider can charge.
There's another factor, which is that photographing a big event has dis-economies of scale. When everybody wants the same standard product, a big company can invest to reduce the unit cost, but that doesn't work well when each unit is essentially a one-off. However, the company has a whole load of overheads that a man-and-dog outfit doesn't, which have to be covered by the selling price.
Just chucking my two ha'pence worth in as somebody who takes a lot of pictures of running events, but NOT professionally. Moreover, I wouldn't even dream of doing it professionally, because it's a lot of hard work for not a lot of money.
The difference between a phonecam snap and a photo I'd personally be pleased with is night and day - to me. You may think differently, and that's your absolute right, but I wouldn't feel happy charging for a picture I thought was crap, and I'm sorry, but most amateur pics (and to be fair, a good few professional ones) are crap by the standards I set myself.
So when my wife is running a race, I'll go along to support her, but it costs me nothing to press the button for other runners too, and if there's no official coverage, I'm more than happy to make those pics available.
What I'll do, then, is just upload the pictures to Photobox, pretty much straight from the camera with no processing other than removal of the completely duff ones. If people want to buy them, I just double what Photobox charge for the physical print, so you're starting at something like 25p for a 6x4.
Of course, I'm not indexing these photos and I'm not even pretending to have pictures of everyone, just those who were in the right place at the right time. I may not have a picture of you; you'll have to work to find it if I do; and it may not be presented at its best when you find it. I'm not doing any real work so I don't have to charge real money for it.
If I was trying to make a business out of it, though, things would be very different! When you have hundreds or thousands of images (and it doesn't need to be a very big race to hit the thousand mark if you're doing it properly), even a tiny amount of work multiplies to a large total. That's time which equates to money, and the essence of running a business is that you have to charge more than your costs!
What I'm saying, then, is that £10 may be more than your picture is worth to you, and that's perfectly ok, but it's not that price because photographers are greedy and trying to rip you off. I sure as hell wouldn't do it for that price!