It was me, Lundafaret and some more people having that discussion and yeah, I more or less agree with you.
Plus you loose the connection with the grass roots of the sport where some pimple headed teen modifies his or her first ever car with a roll cage and some go fast bits and suddenly he or she is a rally driver.
The cost is more or less always what the team building the car has to spend. Sure, a spaceframe would be cheaper, but then you'll have so much money spent on dampers, engines and engine bits that those will be the expensive bits instead.
The budget is what it is and depends entirely on the following of the sport and how good a marketing tool the sport is perceived to be (and how much money the manuf. actually have to spend)!
We can see now that also the cost of the R5's are slowly creeping up with the Skoda being a bit over €200 000 despite efforts made to keep the costs down (the original Ford was something like €160 000) so development will always add costs where it is possible to develop.

