For years the darkweb marketplaces have been using vendor scores to solve this trust issue.
On Nostr, maybe we could do it with badges. You get your stuff, you want to leave a review, you do it as a badge to the vendor. Vendors that have collected a lot of these can be considered trustworthy.
Trust scores are a barrier for new vendors. It's hard to establish yourself. But I think the benefits outweigh the downside.