One interesting use for this would be to get a tattoo you think you want to be permanent, and then when it fades, decide if you liked it enough to get it redone with permanent ink.
Your doubling the cost of a tattoo though and they're already pretty expensive. Wouldn't it make more sense to just be certain you want one before you get it and save hundreds of dollars?
Sure. But how can you be certain? I have no idea what it's like to have a tattoo, or whether I'd regret it. Would I be too self-conscious about having it? Or would I enjoy seeing it in the dark?
I've had one specific one in mind for most of my life, but I don't know if I want it. If I were able to get a fading one, I'd be way more likely to jump on it. The increased cost is nothing compared to being able to decide if I actually like the damn thing.