Since it's just the merchants fair enough, but it's not that unbalanced considering the scheme of things.
If I need a weapon to combat enemy DT, but have yet to find one roaming or need to perform constant repairs to keep it above the threshold.

I can buy one and or replacements from a merchant, and chance my skill / luck against the said merchant without losing every penny just becuase I don't constantly go back and forth toting around heavy objects to earn money.

Improve the A.I of caravan players yes, cap it to three times for three + days, make the merchant charge more buy less yes, remove it completely after a few goes is just a tad silly imo.

One issue of balance neglected is DT and V.A.T.s, still dying to hordes at all levels to kill one foe ( who can magically glitch out of range, or dodge through the blow ).
Still facing NPC's with more health than a deathclaw wearing 15 DT armour, and having a perk granting an extra 15 DT, turning them into a palladin.
Facing 20% damage despite having 30 or 40 DT is anti pc, pro npc, due to the vast amount of enemies you face with semi / lever action or full auto weapons.

There are plenty of unbalanced things in the game, the patch fixed EW, but fixed it for npc's as well.
Most of the other fixes I assume fixed likewise for both at best, or more likely to balance the pc's skills lower to stop godhood.
While keeping those designed to challange heavily, if not pigeon holing a certain playstyle entact.

This is just my feeling towards balance, it's a bit of a rant I apoligise, just balance does not automatically fall under removing favourable things towards the player.

I prefer my single player games to have reasonable limits. Thank you, Bishop, for the patch update. I still need to load it on my 360.

Its kinda related to this, but instead of capping games so you cant play them why not just let people play but gain no money ? Just give some worthless currency. Its strange going into casinos and not being able to gamble.