Even the low-quality frames from craft stores tend to cost significantly more than a cheap poster. A poster is just a big piece of printed paper.
I fully acknowledge I may be asking too much. Just saying that if you can hit that price point I will probably become a customer. No idea if I'm unique.
Doesn't sound like what OP is going for right now - seems like he would have better margins to start out on the high end. I don't have experiential data but I've read in many places that low-price products can have more difficult consumers because they expect so much for $20.