Absolute max of 2 quid per kilometre. That rules out the Great Manchester 10K or whatever they call it these days. I'm pretty sure that was close to 50 quid this year.
This route goes past my flat every year so I usually end up watching it but never been compelled to do it at that price. People at work who run it each year are stunned when I tell them how much other races in the city that are organised by local running clubs are.