Had this happen with a 1-2 friends repeatedly. Like they would borrow my tupperware to bring leftovers home then call me to get the dirty tupper from their house. We had similar incomes and expenses. Escalated the shaming. Started with polite nudges to bring things, got to telling them to bring something next time and to not leave with leftovers, and eventually told them they were making this their hill-to-die-on in our friendship because they weren't welcome at the cookouts anymore. Smartasses once each brought one set (like a spork with a napkin) of plastic-wrapped disposable cutlery and a generic red plastic cup. Fuck that.