Wirelessly posted (The Roaming Phone: Mozilla/5.0 (iPhone; U; CPU iPhone OS 2_1 like Mac OS X; en-us) AppleWebKit/525.18.1 (KHTML, like Gecko) Version/3.1.1 Mobile/5F136 Safari/525.20)

I've never seen that one before. What location are you referring to? Most other locations do either an extra $250 or so or 15% above the cost of the rental. 10% of the car's value is probably $1-3k, depending on the make and model!

Unfortunately, it's not easy to get around those kinds of requirements--rental locations put them in place for a reason (to screen out risky renters who wouldn't be able to pay for damage or extra days/fees, etc.), but that said, 10% of the vehicle's value is quite excessive. I would call customer care to clarify the policy and register a complaint (800.283.0898, option 2 and then 0). If that doesn't lead anywhere, I would recommend contacting the corporate offices--I have their number on file somewhere but lot handy, but if you search for "Gary Paxton DTAG," you should find it (918 area code). That should get the right number even though he recently retired as CEO.