Got ya beat, $0. First time I've never touched a vehicle that I've owned but I'm keeping this one stock for a little while, or maybe my full ownership, who knows.
I've had 4 rams and have always done at least a few things to them to make them more to my liking, but for some reason I'm just not tempted with this one as much.
Edit: I guess I have to correct the $0, I did buy the back seat hammock and door covers for when we take our dog with us. So I guess I've spent about $60-70 on "customization" albeit not anything all that fun. Although having the dog with us is of course great!