When you're actually charged
Checking out and being charged are two different moments. What happens in between depends on whether the order is pickup or delivery.
Checkout puts a hold on your card
Checking out authorizes your card for the order total. The amount is only held, and the hold is released if the order never goes ahead.
An order for a date far ahead works differently. A deposit is charged right away, and the rest goes on hold on your card closer to the date.
A pickup order is charged at ready or at pickup
For pickup, you are charged when the seller taps "Mark ready for pickup," or when you confirm pickup yourself, whichever comes first. If something still needs weighing, the charge waits until pickup. If neither happens, the order completes on its own a day or two after the agreed pickup time, and the charge is taken then.
A delivery order is charged at the drop-off
For delivery, you are charged when the seller drops off your order and takes the drop-off photo, or when you tap "Confirm delivery received" if that comes first. Your confirm also pays the seller. If you do not confirm, the seller is paid 24 hours after the drop-off, unless you report a problem.
There's no separate buyer fee today
The order total you're charged is the subtotal of what you ordered. EZH's commission comes out of what the seller receives, not something added on top of what you pay.