Interesting, I could sure try. Something that cheap would take a bit of effort - hardware itself is very cheap (laser cut plastic chassis, some screws/nuts, and a couple 3D printed brackets), it's always the servos that bump the price up.
I still say you should go with PCB FR4 material or something like that; it's fiberglass, and very strong. Your PCB routing (cutouts) and circuitboards could all be done by the same company; if you laid it out right, you could do a slot-tab construction with solder joints to hold the whole thing together (maybe with some extra wire bracing for certain areas). That way, you could make the whole chassis "3D" for future prototyping (add proto-holes to the legs, for instance). It should be real cheap to do; much cheaper than acrylic and assorted hardware, probably.
I could go for some micro servos, those go for around $15 minimum though... that brings price up to at least $180 for servos alone. Of course, mass production lets you drop the price per servo when buying in bulk so technically that could be dropped to maybe $140 or less. I would argue something closer to $200 would be possible at a minimum -- do you think that would still be attractive, cr0sh?
If you're going to do this, you'll likely have it all fabbed in China somewhere; go on ebay, look at the small 9g servos on there. I pulled up a page where they were under $3.00 each - that's the price point you'll want to shoot for.
As far as a prototype is concerned, you'll want to do this. You could probably do one in acrylic, first, with an eye to translating the design to PCB material; work out the design kinks, etc - then you'll have a viable design for sale.
