Once you have a good amount of users testing, its not that difficult to get free servers from the ISPs. The secret is that on-net servers show testers better performance than off-net so every ISP wants to contribute the speed test server. If they dont do it they are shooting themselves in the foot by routing their traffic to competitor networks and getting test results behind their peers.
Whats even worst then your competitors can claim awards for the Fastest ISP and your marketing people are furious!