I'm also amused that I seem to be incapable of ever building up any kind of significant caps bankroll.
Every single time I complete some big dungeon and roll back into town loaded up with "phat loots" I'm like "Sweet - THIS is when I finally start to get ahead - I'll sell all this and finally have a nice pile of caps."
But instead, I always end up trading all that junk for... a different pile of junk. :lol :lol I always go through the same routine - I select all my stuff for sale, first. So when that's finished, I'll see that the transaction is like 
<--- 645 caps or whatever. So then I look at what they have for sale, thinking I'll pick up a couple things, but still end up with some huge stack of caps. I'll buy a couple stimpacks, maybe a new piece of armor, maybe a schematic ingredient, and before I know it, the transaction now reads 
<--- 23 caps and I'm like 
