That's not quite how I understand the system works. My understanding is that the counties pay the ECB and then get to set the ticket prices and keep all the match-day revenue, but also get to risk losing money if sales are poor. That's part of what fucked over Durham, and the reason counties have handed back tests. It's also part of why some tests in the past have been eye-wateringly expensive - Glamorgan's Ashes test being a case in point, where most tickets were £100 plus.
They've switched from an 'internal market' Thatcherite system with sealed bids to fixed prices for test matches, and some counties, notably Warwickshire, have reduced their ticket prices somewhat, but the system remains one in which the counties pay a fixed sum and take on both the chance of making money and the risk of losing it. The likes of Surrey are the biggest winners in this situation - guaranteed big sales due to an accident of geography.
Durham were effectively dismantled for doing exactly what Glam, Hants, Yorks and Warks have also done to pay for test ground improvements. More than that, Durham were instructed to act that way. Yet we're very nearly back where we started - with the six traditional test grounds dominating test matches. Meanwhile, counties that have developed their grounds in a way appropriate to a county ground, who ought to be models for the likes of Glamorgan or Hants - Somerset, for instance - get fuck all recognition for it.