I could hammer out a tri-poly, dynamic mesh without texture of that dress in under an hour.

But I wouldn't sell it to you so that you could sell it.  I would sell it myself, or enter a partnership with you if you wanted to texture it and/or retopo the thing into quads and rig it.

 

I don't think anyone is eager to model something only to part with it and watch someone else vend it in the marketplace infinately without getting a cut on the back end.

So, the hourly work I would probably ask for 20 dollars.  If you want to market it in the marketplace...I'd estimate that dress would probably sell about 100 units at minimum market price (5, right?) so that's 500 dollars split with RO that's 250 and I'm going to need 125 of that on top of my hourly....so

145 dollars gets you an untextured, ungrouped, unrigged tri-poly mesh of that dress.