40k ?? It's hard to believe... anyway still it's trip made by car which can be bought only for caps! I can't see anybody walking all way from VC to SF (with this little detour). I think you were pretty lucky or just have great timing. The biggest amount of caps I ever seen in one trader was around 12k in Gun Runners. If those damn TC gangs could spent some caps in traders... it would be whole different situation.
I started in VC and traded for around 10k there.
Than I took the train to the Boneyard and got 2.4k at the station.
Than the train further to SF where 1 trader had 17k and 3 others also had several 1000 caps.
Than a tour to Redding, back to SF, from SF to the Hub, Junktown, NCR and finally back to VC.
On a side note, I got 10k yesterday in VC alone.
I think the big gangs aren't looking at npc traders, it's too inefficient with the amounts they need.
Some probably have a few fixed suppliers and they'll probably check out the trade forum daily.
If you can get .223 or 5mm AP ammo, psycho, buffout, etc. in large amounts and offer it on the trade forum, they might buy it.
You might actually be able to get more than you would get from traders, so it's a win/win for both.
By everything I meant everything from shops. Buying absolutely everything with junk items would be goddamn horrible in terms of workingl economy. It would basically mean that every last hope of player interaction in economy would be lost.
But selling junk items to npc traders is what would happen in a Fallout like world.
Things like ammo could be kind of a currency.
NPC who offer professions could ask for items, though be it not like the guy in Adytum asking for things like 10 green condoms.
For instance:
A certain amount of HQ ores, HQ minerals, GMP, Adv. gunpowder, HQ alloys for SG/BG/EW/Armor/Explosion levels, but depending on where you get the profession.
BoS might instead ask for 5mm AP and/or AP rockets too.
Enclave might add MFC to the mixture.
Docs could ask for meat jerky, med gel, chem components, etc.
So not the low quality easy to get stuff, but the stuff that's a bit harder to get.
Perhaps we could add some kind of supply/demand bulletin board.
Logically it would be placed at the default entrance, another option is near workbenches.
In SF and VC we could use a terminal.
VC could actually have 1 for the courtyard and 1 for the inner city.
Entries would be removed after 24 real-time hours.
Sellers should be able to name what they want as payment.
It might be hard to code, but it could add some player interaction.