I've generally paid 50-200 gold for my tattoos. There does not seem to be any rhyme or reason for the prices. I paid the same amount for a simple lip tattoo as i did for a more elaborate body tattoo. Grab 200 gold and you -should- be fine. Assuming you are not getting something with a crazy long description.

You can always wait for a free one as well. In the past they have had festivals where the sponser of the festival has picked up the cost. I believe it was the human council festival that did that one time. Staff has also done them in the OOC inn. Its an OOC type thing but you still will be responsible to pay for it.

I'm not sure that is the kind of information you were looking for. Hopefully it helped.