Your car rental requirement has nothing to do with the cost charged for the tour. You can bring your own towel. And the $125 is appears to be for motel luggage valet service. Tent charge is optional and not out of line with what other supported rides cost. Bring and pitch your own tent. The add-on services are usually contracted out to companies who need to make a profit.

And if you think it's expensive, look at something like Cycle Oregon, of which I have done four. The base price with meals is now probably over $1,000. Add another $110 or so for bus transportation to and from the start. Flying from the east coast costs some coin, including airline bike fees or shipping, and I have needed hotel rooms the day before and the day after. Tent and porter service, which I have never done since I don't have a problem pitching my own tent, is probably close to another $500.