We visited Oman in 2011. We rented a car, drove north thru UAE and then crossing back into Oman near Al Ain. We had to pay the Oman visa fee both on entering the country and on returning from the UAE. We paid 200 MR (about $60) for each visa. It was a surprisingly tedious and slow process to enter Oman from UAE. There were passport formalities on both sides and a no man's land in between. We had to get out of the car in both countries. In UAE, our passport had to be stamped out and in Oman, our passport had to be stamped in after paying the proper fee. But they sent us back to UAE because they couldn't find the stamp in our passport. It proved to be there, so if you have a heavily stamped passport as I do, take a sticky to mark the page with the stamp.

I believe we also had to pay for additional insurance to be able to take the rental car between the countries. I distinctly remember we needed additional paperwork.

The best part of the drive was seeing camels along the road, multiple signs to camel races, and seeing camels being transported in trucks. We also went to the camel market in Al Ain.