Go to the site that is putting this bunk out and they are saying that is the average contribution.
And which site would that be? ABC News? The Wall Street Journal? Politifact?
As near as I can figure, what you are are referring to is some obscure article on a blog from the 2008 election saying that he had "the highest amount of military donations and the average was $500". That was then -- and I agree, in all likelihood bogus. But this is now and it's real.
That Ron Paul has the highest amount of military donations of any candidate in this election cycle is a an accepted fact -- even by his Republican rivals.