You can check out mine. I usually go for between 500 and 1000.
http://www.menewsha.com/forum/art/ar...656-comic.html
But for first timers, I'd say go for a couple hundred discount. If you're pleasant and negotiate well, they'll tip you. Just don't expect it, because that's not nice.
Or you could take the straight forward approach. Say, chibis for 500, head for 500, waist for 700, full body 1000.
Just make it you. :)