My two reactions to this argument...
1) I don't think it would have a huge effect on demand for MNs (though I could be wrong). My rationale is that $2,500 is not a lot of money... at least there are a sufficient number of people out there with $2,500-3,000 to allow the market to reach equilibrium already. If there happen to be a few people on the sidelines because that is too much money for them and they end up entering the market through a share in a MN and this drove the expected frequency of reward down for the remaining MNs, I suspect you would see a near equal number of MN operators exit their MNs (having no real effect).
2) A correlation in economics would be a stock split. Yes, it would make it so that the cost to get into the stock or MN would go down, but the payout is also lower. So when a stock splits, it might move up a little bit, but not much of an effect. You certainly aren't going to see us go from 800 to 2000 masternodes overnight. With stocks there is sometimes a gain of 5% or something, but you could argue that much of that gain is simply coming from the signals management is saying about their confidence in the stock by making such a change, not due to the "affordability" going down.
3) DRK has already been as high as what? $16,000 for a masternode? If your theory were correct, wouldn't we have seen a huge spike in the number of MNs already when the cost dropped to less than $3,000 today? It really hasn't moved much. This is further evidence that the MN network is acting as any economic asset with a return on investment would. The absolute cost is largely irrelevant.
So for me, the evidence is that trustless MN shares would be a lot of work without much, if any, impact on the number of MNs. It also introduces the complexity of how to make sure the trustless solutions deployed take the proper steps to secure the servers properly? So in that sense, you still have to "trust" the MN operator to do the job properly. It's not "trustless" in that sense.