it's hard to compare S2000 renting prices. those depend on many factors - car (brand, evolution, level of preparation), team (it's name/history, spare parts, engineer, etc), plus tires incl. or not, insurance, deposit or not, one event or few, tests or no, etc, etc.
but some time ago it was surely more expensive than it is now.
and surely S2000 cars need rebuilds more often than 1000kms, OK, engines and transmissions are often above 1k kms (but there was some evolution of 207 engine with only 600kms limit). But even if you do less than limit you often need to look inside the box to check after some "issues" during the rally, to change ratios for next event, etc, etc. Dampers usually needs rebuilds more often than 1k kms, brakes changing/rebuilding also more often. Plus rebuilds of crossmembers, arms, uprights, shafts and many, many other parts. Plus some body parts like bumpers, sills, etc are often damaged after very few kms.
So it's not that easy to earn money on renting S2000 cars, of course it is possible, but not that almost all the money which customer paid are left for you to put into your pocket.