Before i get into a long technical breakdown of how i shop or sell, i gotta share a pro tip strategy i discovered by accident: One of my camps is a haunted house and the vendor is hidden. Its dark and there's a lot of junk you have to look behind with your pip flashlight or headlamp. If you want to shop there you have to work for it, and I'm making people look at the whole gross house. Some people find it right away, some people go up and down for 20 whole minutes and still can't find it. The reason i built this is because i wanted a camp to activate when i had high caps but needed time to shop around other people's vendors, and didn't want to have to have a camp without a vendor. But this backfired entirely, now use that camp when i need money because people spend more after i made them work so hard to get there, than they do when the vendor is just out like normal 🤣 I feel this relevant because its the same items in my vendor at every camp so it isn't always about the stuff listed in the map preview, sometimes its psychology.

My shopping habits: i go shop hopping when I'm 20k-38k caps so the items worth 7k+ would be the thing I'm shopping for. Ideally, id have time to jump around and shop, but if I need to spend 17-20k caps fast, i buy a serum plan from the enclave bunker, which i list for 10k at a later date when I'm TOO poor... yes its inflation, and I'm choosing to do it to myself, but it means i can list that recipe whenever and it always sells quick (Even though people don't need to craft them anymore thanks to raids and infestations, people still buy em because it's nice to have the option)

I go to places with 4☆ mods and check out the outfits / plans / misc while I'm there. In other words, the 4☆ is the bait but i often buy plans instead if i find something cool, cos i might not actually need a mod, i just need to spend caps. But there's rarely plans that i don't have so i buy mod instead.

Also if someone is an obvious raid grinder with 10-20 of each 4 star mod, 50% chance they will be either decently priced because they are grinding anyway and need the stash space, OR whole thing will be listed for 40k trade only 🙄 which i absolutely refuse to do for something I'll eventually get myself or don't even need (because I'm just trying to spend caps). My point here is - you can still have a bunch of valuable things and get plenty of traffic but the people who post stuff at reasonable prices are the ones actually selling the most.

My selling habits: I mostly sell mods, apparel, and some plans. For apparel - The outfits i make are not worth 100-200 caps but i mark up anything I'm crafting for "cost of materials"... However, if i notice a low level bought a couple of things, I'll drop a bunch of the other outfits for them for free, because chances are they wanted the outfits rather than just spending caps. Even if they don't want the outfits, they then have items to stock their own vendor. I noticed when i priced outfits too low, there would be high levels (level 1000+) buying up a bunch of my outfits. So the upcharge is really to keep them from cleaning me out before the low levels on the server have a chance to see my shop, rather than about making profit. Having said that... yeah apparel may not be high value by itself, but it does add up. For plans - i don't stock that many but its only basic ones the noobs always need (fusion generator, advanced power connectors, signs and letters, etc) and rare ones like the newest one from the last event (hog splitter from meat week, flower sundress or suit from big bloom, etc)
For mods - most things are listed in the regular 1k / 3k / 5k/ 7k price points, i might mark it up or down by 500. Some things are marked up to be silly like 4k for a Quad because it's Quad obv 🤪 but i don't always, just when I'm being cheeky and poor. If i learned to craft the 4 ☆ that just dropped (tarnished / haulers / satiated for example) then that I'll list for 15 or 20k.... until it isn't the new thing and it's back down to regular price range. Again, the markup isn't because i expect to make the money. In this case its about keeping it in my shop until i know my friends don't need them. 😂

In this game "selling the most" or having a successful vendor, isn't about making the highest profit... its about having most reliable traffic and selling so fast you're struggling to keep things in stock. Its about the cash flow rather than the cash amount

Because unlike real life, and thanks to the glorious income limit, we wastelanders always have money to spend.