Cant help much on the skis, but as far as the bindings i paid right around 200 for new freerides after shopping around A LOT. It looks like my boots are similar in terms of entry level at boots with three buckles rather than four. I paid about 300 for my boots again after shopping around quite a bit. Used skins I personally wouldnt pay more than about 80 for unless they are practically brand new. New skins range from 130 to 170. If i were in your shoes i would try and get the bindings for 100 or less and the boots for 150 or less. Add that to the skis and you would have a very reasonable entry at set up imo. A note on the skis, i bought used skis from a ski area that were lightly used, no core shots etc. The skis retail for 900 w/o bindings and i got them for about 300. Maybe that gives you a reference to go off of.
I went the Craigslist route and wound up paying $375 for those same bindings, a pair of Black Diamond Mira skis, and like-new skins...everything in top flight condition, just a few years old and used about 3-5 times. I've found similar deals on craigslist, so if you are patient there are great deals to be found!
For that whole set up, you should expect to pay around $300-400 for it all. But then again, I would offer you $200 and go from there.
BTW, If you buy that set up, ditch the skin savers. They are junk!(the G3 type, the red ones) They end up getting melted by the skin glue, and meld into the skins.