This directly competes with Revel POS: http://revelsystems.com, though pricing isn't visible on their site, I would believe that Square's offering is also cheaper -- at least to get setup.
$99/month, no startup costs, competitive credit-processing. Also has a much more robust featureset than Square. It also makes your storefront work on GoPago's mobile app, which is something that no other modern POS system does out of the box.
Disclosure: I work at GoPago.