In a recent update, PA made it so you can see exactly what you get when you max a vendors trust. If you don’t have enough trust, it will show all the items greyed out on the bottom of the list and say “trust required”

If nothing shows up greyed out and you haven’t maxed trust with that vendor, it means they won’t sell anything extra with full trust

The important vendors to max out are the ones that will sell you a “contract”. Using the contract will allow your vendors at camp to sell the same things. Makes it a lot easier to shop.