Is it boring to scroll NPC's stock list and don't know it's scrolling or not, because list don't changing, because you see there 483765384 radios or 5476834 10mm pistols or 3453458 BB guns in a row. Or when you see 10k needler cartriges and 5k BBs at shop, you think what an idiot must be that trader to buy this all.
Suggestion:
If trader has more than 8 units of the same type of weapon or more than 800 of the same type of ammo (80 for rockets) or 40 drugs/medicaments, he'll say "No thanks, I don't need more." or buy it, but for only 10% of it's price.