Curious if anyone has any experience running a print on demand or e-commerce shop.

Like paper? Printing maps/reports/brochures etc? Used to use a service like this in Houston easily spent 20-40K a year with the printer for an office of 30 people. Since 2014, I've used that service for less than $1,000.

No one wants print materials anymore (reports) I'm sure brochures are still being printed. Dunno if this is even in the same field of what you're asking about though.