We work with any brand that has a brain! You're very right, if you don';t have post purchase locked in, you're making about 10% less than you could on customers you already have. That's literally free money you're ignoring. The service we provide is actually free and commission only because of this, it requires no money to implement and test, and post purchase upsells work for pretty much every brand except for exclusively high ticket stores.
Tell me what you do to help with product discovery and search. My mother is starting her own store here soon we could use some tips. She's going with luxury wine coolers or something along those lines. Unsure if she's quite locked in her niche yet and any suggestions would be great too.