I think $60 is low on a full sized skid steer. After I finished typing, I almost edited it to $85, basically I figure $35+(1/2 your HP). I didn't look up his machine, but I'm guessing 85-95 HP. If you buy materials, don't forget to mark up for sales tax, 15% profit, and profit on top of the trucking. I don't see the client getting many people to fool with it for less than $2000.
Edit: I did look up spec, its an 85 HP. There's nothing magic about my number, I just tried to find a good way to price tractors/skid steers/CTLs based on size, fuel consumption, and depreciation.