Up to $400 per any single transaction and up to $250,000 in total transactions per year—or approximately $21,000 per month. Swiped transactions over these limits simply cost 2.75% per swipe.
$21,000 * .0275 = $577.5 in fees.
I would love to see more Square adoption. In Charleston, lots of cart vendors (hot dogs, popsicles) use Square, as well as many vendors at the farmers market.