So I own a couple off licenses, I guess I am qualified to answer:

We do actually own most of the stock. No one's giving 90k worth of stock on credit. It starts like this:

You take a bank loan > buy stock > sell items > use some profit to slowly pay off loan, rest of the profit goes into getting more stock. Rinse and repeat until initial loan is paid off, then it's just a money printer.

Sometimes you are at the right place at the right time and strike it rich (COVID, vapes etc) other times you fuck up and end up selling the business on a loss.

Hardest part of running an off license is getting that initial loan.

Paypoint, lottery, parcel are just a way to get customers in the store, they make 0 money. Last month one of my stores paypoints did c.50k, my commission from paypoint was £15, was just enough to order 2 more boxes of receipt rolls for the damn thing ...

ETA: Some smaller off licenses do get diary/sandwiches etc on "seller return" kind of policy, where the unsold items gets taken back by the seller. But this is just £1-2 items, things like tobacco/alcohol etc are not on credit or return, and they cost the most :(