How many sales you actually need each month before you start making money — card fees included.
Fixed costs are what you pay whether or not you sell anything — your EMPIRE plan, domain, software, rent, insurance. Card fees of 2.9% + $0.30 are deducted from each sale automatically.
Contribution per sale is what's left from one sale after the cost of the thing you sold and the card fee. It's the amount that goes toward covering your fixed costs.
Sales to break even is your fixed costs divided by that contribution. Below this number you're losing money for the month; above it, every sale is profit.
If the per-day number looks unrealistic for your audience size, you have three levers: raise the price, cut the unit cost, or cut fixed costs. Most people only ever try the third one.