In some ways, loss leading can be done in more or less ethical ways. For instance, a small mom n pop hardware loss leading on lumbar or hammers and taking a reasonable profit on ten penny nails. Or something, maybe a better example is the Costco 1.50 all beef foot-long dog and soda but their memberships are reasonable profit for those who would go often enough and buy enough to make it worth it. It's late and I'm tired, I hope you get the general gist. But yes, doordash is just double-dipping on the sleazy. And maybe loss leading isn't ever acceptable, but I'm simply unaware/haven't thought of reasons that make it so. I'm willing to hear any argument against any of it, though.