I expect a small site that undercuts the top Google results by 18% with a sign-up discount probably isn't profitable on those orders, so blocking agents would save them money - it's not like someone using agents in that way is going to have any loyalty to shopping from that site in the future.
Yeah, I mean if that's the case, then said small sites are probably headed for extinction, and agents won't have anything to work with other than whatever the top Google result is anyway.
And yours and other's agents will probably remain an insignificant and invisible customer base anyway.
My crystal ball is as good as anyone's, but if "agentic shopping" ever becomes mainstream, you can be sure that the vast majority will ask their phone (i.e. Google, i.e. Google Shopping) what the best price is anyways.
Sure, Google could be their agent, or ChatGPT, or Claude, or whatever local model the person is running. The big guys might all have the results cached so they don't have to rerun the crawl. Whatever their choice of agent, it seems pretty clear that almost everyone's going to use them, they're way too useful not to.