Great use of space for vertically inclined photos.
Speaking of which, are you shooting horizontally as well to accommodate the 3rd party sites like cars.com, autotrader, etc.?
I agree with Ryan Thompson's advice re: uploading. There are services/software out there that will enable you to manage and upload photos for all of your clients. Autouplink and Netlook are a couple providers that license their software out to independent operators. IIRC, cost is pretty reasonable, around $200/mo. I really like the Autouplink software, it runs on an android tablet and you can connect your camera via a USB2go cable and upload directly while out on the field.
As for pricing, I think your range of $30-50 sounds reasonable. You have to keep in mind there are larger-volume companies out there who subcontract this work. That should be less of an issue for you since you are focused on a niche product where quality of work is absolutely critical. If you can take your service to the next level by adding quality descriptions and window sticker, $50/car is a fair deal. Maybe start higher since the dealer is going to haggle you down anyway lol.