Right but it saves labor in the office, and the cost of dealing with bounced checks, and the accounting is much easier when payments are made online, so the landlord ought not put the gross cost into the rent. It’s cost and savings to the landlord, likely netting out to nothing, or a savings on the online accounts.
In a small restaurant, I understand cash discount. They are gonna have to count the drawer at the end of the night either way. In an apartment building, no. That’s charging people for saving you time and effort, it’s a junk fee.