Pricing for each banner is case-by-case. There is no getting around that. But you also want a general idea of how much this will cost you. I get it.

For the majority of custom banners, the rate starts at $135 a square foot.

This is very, very malleable. Depending on detail, complexity, materials, and (last but not least) size. But, for a place to start, start there. I am more than willing to work within a number and believe that art should be accessible for all budgets.