So, my kids were watching "My friend Flicka" a classic movie about a family that raises horses and I happened to overhear some horse trading.
 
Oddly, everyone in the film agreed that the price of a horse is exactly $500.00 and so instead of haggling over the (non-negotiable) price they wheeled and dealed by offering horses with varying abilities. E.g. "Why buy a regular horse for $500 when for the exact same price you could have a mentaly-unstable rocket horse?"
 
It got me thinking about the implications of that kind of bartering on gameplay. NPCs already do stuff like that when they offer a quest to whoever finishes the quest fastest. And the PC's do the same thing when their 1 GP buys them any drink in the house. And when they buy the best they could afford, it's basicaly the same thing: the amount of money they spend is set but the kind of gear they get is negotiable.
 
Anyway, does anyone have any insight or objections to this style of barter in game?

Most games I've read that require the itemized purchase of equipment and sundries are pretty vague about the relationship between quality and expenditure, unless the gear has obvious combat utility. If I buy a masterwork sword I'm gaining a mechanical advantage in exchange for my additional in-game resource outlay. A fine meal gets me nothing beyond a a flavourful description, if the GM is so inclined.  

If the negotiating style you're proposing is to have weight then it needs to go beyond this. One idea that occurs is setting a quality value for goods. By default the QV would be that of it's gp/doubloon/space shekel cost, with superior and inferior examples being higher or lower. As coins are subtracted from the PCs coffers the corresponding QVs are added to their perceived wealth. The higher ther PW total the more likely they are to be offered yet more quality goods, attract skilled retainers, receive land grants and be offered prestigous quests. They now have now dual incentives for spending money conspicuously and haggling for the best quality items.

In my Fantasy Game, the quality of your supplies usually geneates a special modifier.  

So if you ate at an exceptional inn and rested there, you probably get a +2 MOD for everything the next day (+1 the day after).  If you had wonderful trail food prepped for you  +2, (adjusted for -1 sleeping under the stars).  When you are cold, hungry and miserable, -2 MOD.  

This was the Qual MOD and it was a track from +3 (which nobody ever reached) and -3 (which was seldom reached), with most things being +1, 0 or -1.   (Yes, high peek bell curve)

What did this mean to my players?  They were always looking to spend coin on the best darn inn with the best darn food... as now they had incentive to do so. My dungeon crawler who used to eat trail rations in the city because they were cheap, discovered that silver pieces for positive mods was a good deal (in the end).

Now clothing, grooming, and style, have always been modifiers to social roles. Criminals, though often grimy and not styled, have their own look, which is often as expensive to maintain as a nice set of clothing.   So quality of clothes/ style/ grooming adjusted for the "stage" (High Society, Business/ Middle, Low Society, Rural) was an adjustment to all social rolls and reaction rolls.   This was the Style MOD.

There were practice MODs (time to practice your craft) and Upkeep MODs (keep your gear in good order by spending time and some money) as well.  Our late starting fighter type spent wayyy to much time practicing (keeping a pretty regular +3 MOD), because it was the only way he felt he could "keep up" with the other more experience fighters.
While this looks like a lot of modifiers, once you get them all "assembled" for a given day/ time, it is just one flat modifier added to base rolls

These all have two design purposes.  One - it parts players from their money and poor players are motivated players. It also parted them from time, as they had to spend time to keep many of these modifiers at their highest numbers.  Thus they began to realize should I practice and keep my +2 or should I go look out for this possible adventure that may be a red herring.   Two, it added a motivation to get the best and work at things.  

So players would work at bargining for things. They would work for reducing the price or aiming for one shift in quality.  Usually this was a quick contest, but sometimes it was a task for bigger items.

Those without social skills would often try to "buy a modifier" by buying style.  Once that modifier started, they could get the better things for the same price, which let them be better, which let them earn more stuff, which let them get a better mod.  And they would defend their stuff and position, because they had worked hard to get it all.

What?

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