Wow! That sounds awesome! I would totally pay it!
Our dog parks are all county funded (through bonds for parks and rec stuff), so we pay for them through our taxes but there is minimal upkeep (they remove trees that fall in storms) and anyone can come. $500 (and really, if you go for 5 years, that's only $700 or $140/year--$2.70 per week) seems reasonable for all that you get.
I am jaded to high prices though. Day care here is $30/day, a dog walker is $20 for a 15 minute walk, 6 weeks of training classes are $200, etc.