Can you make a suggestion on a private transfer from the Nice airport to Hotel in Arles. I'm not really looking for a tour, just transportation. Something $500 or less.
I'm sure you've had a look at trains and one-way car rentals and can't do it for some reason but I'll ask anyway!
Else, my first step would be to call Taxi Riviera, the official Nice taxi company, and see what they say. What you're asking for seems feasible for $500, given that it costs about $250-300 to go to Saint Tropez by taxi and Arles is a bit less than twice as far, time-wise.
You could check out this company that we have used before - https://www.solhop.com/nice If you want an exact price or can't see it online, I usually email them with what journey I want and they reply with a quote. I've always found them to be very reliable and super helpful.