Where is there a store in this game with somone who has more that 250 caps???

i dunno but my little brother just bought this game and its boring as shit

i can't think of any now but you should use chems or ammo as secondary money. my current character has over 5000 shotgun rounds but has never shot a shotgun.

1. you can sell all items at any store so don't think you have to sell ammo to ammo merchants.
2.The best merchants are the caravan merchants once you get to canterbury commons and talk to uncle roe *commons is the place the super human gambit quest takes place.* and invest in them to the highest amount, once invested they have some of the best weapons, ammo, and items for sale, have some of the best repair abbilities, and carry many many caps on them.
 
 http://fallout.wikia.com/wiki/Canterbury_Commons

No Idea dude, I've never had the desire to sell 250 caps worth of stuff. 

The Caravan merchants usually have the most caps, specially if you invested in them through Roe at Cantervury Commons.

Its never caused a problem for me and Ive beaten almost every quest in the game and played 4 of the 5 expansion DLCs.