What to charge for a custom script?

[Vulpinus]

I've been asked to write a custom skin texture applier for a mesh body*. I've no idea what I should be charging though. I've never done a commission like that before; I usually just make things and script them. Well, not in SL anyway. I can't ask what I would for bespoke work in RL, lol.

What would be a fair amount to expect, without selling myself short? The scripting is easy enough; will take more work making a nice-looking HUD in photoshop to be honest.

It's not likely to be a huge seller for the customer. It's not the latest (insert your favourite mesh maker) Bento head or anything like that. More a niche market.

*the standard systems like Omega are not appropriate.