There was a discussion of ARIN at ISPCON where Kim H. explained the
funding policy in great detail to the people present. In this case
the
$2500/yr is not for each /24 registered but an annual fee paid by the
ISP to buy service from ARIN (for one year) for their overall address
allocation. If your total allocation is > /24 and < /19 then you only
pay
$2500 for that year. If it it over that then you pay for whichever
tier you
fall into.
People who have /24 - /19 should get IP space from their upstream. It's
a lot cheaper for an upstream to pay X,000$ and charge based on the
smaller allocations (a big money-saver - turns out to be like $40/yr/"C").