The just sell the machines, or lease them. A lot of smaller operators buy in bulk from Costco and use that to stock the machine.

Most cost-effective way would be to browse for an old used one on ebay, should be like $500-1k if you’re in the US.

Like the other poster said, fill it with products from Costco, the only issue is packaging things like single use detergent. You’d probably want a box or something for pods or powder so they don’t get damaged.

You could also use these: https://www.amazon.com/Tide-Travel-1-Load-Packets-Pieces/dp/B001S4C730/

Looks like they’re a bit over $1 each, so sell them for $1.50 or $2 in the machine. Don’t confuse them with the sink packets which aren’t for machines.