There's been much talk of this here and elsewhere.
One counter argument is that if we pay for LARS then it MUST be provided, whereas at present the ATCO can tell you to b****r off when the number of blips on his screen exceeds his trade union quota
(only kidding about the trade union quotas)
Whereas buoys don't have that problem. And to be honest, the "GPS is good, GPS is bad" argument was done to death in sailing some time ago, and if sailors had to pay for buoys they would just not bother and use a GPS to ensure they don't hit anything. You don't have to register a boat, and no training is needed either!
I can't see how GA could possibly pay for LARS, or even a significant bit of the cost. There are nowhere near enough GA planes flying to raise any 7 figure amount.
Mode S has the possibility, implemented free of charge in the USA as a carrot to get GA to take up Mode S, to receive traffic info from ground based radars and display it in the aircraft. But not here.