Being a new DM I'm still in the process of constructing my own methodology. I do this by cramming my brain full of random tables, house rules, scraps of painting, poems, and prose and regurgitating what is useful during play. I keep what work and discard everything else. In between sessions I comb back over what I liked and find ways to streamline it. My players, also new to the game, have been thankfully forbearing.
One thing I keep messing around with is the currency. How much treasure is worth, what kind of treasures are found and where, what kind of items are available in towns.
I dislike my players strolling around with hundreds of shiny gold coins and jewels in their pockets, especially at lower levels. I want them to be struggling, sleeping rough, on the verge of starving, bouncing from one windfall to the next, desperate to stay afloat. This harkens back to Dying Earth. Cugel is swindled out of his money at every turn, just as he swindles others. He haggles over the value of every single terce, and even so spends it with wild abandon in the next breath. I want this same frivolous feast-or-famine play in my own games.
My own players are a parsimonious lot, hesitant to even spend Gold on XP. Even when they go a-carousing they cautiously prefer to roleplay the entire night instead of rolling tables! It's hard to cheat them as their eyes are sharp. There are ways.
CURRENCY
Using lower currency numbers makes each and every coin feel much more valuable. A tool such a 10' pole or a pickaxe might cost a single terce. If an inn costs 4 terces and you recently sold a gold brooch for 16 terces that's a quarter of your earnings!
What even is 700 gold coins?
We play Knave, which uses an item slot system based on Constitution score. My players keep track of their items using index cards. They enjoy drawing the pictures on each card, passing them around to each other, or piling them on the table when they make an item cache in the dungeon. Different items take up different item slots. A suit of plate armor takes up 5 slots. 100 coins take up an entire slot. I usually fudge it with small treasures like jewelry. Larger treasures might take up a whole slot.
The limit on amount of gold they can carry is important. They need those spaces for useful things. It's better to spend or hide the gold than to have it weighing you down.
Gilded tombs do worms enfold
I don't want to tell my players outright how much an item costs. I don't even outright tell them if an item is magical. I want them to use their judgement and decide what is worth lugging out of the dungeon.
Each Item has a Die value, d4 d6 d8 d10 d12 d20 or d00. When the player tries to sell this item to a vendor I roll that die, modified a bit by the Trustworthiness of the vendor (aka I fudge it a bit based on the vendor's personality). If the player doesn't like the number they can attempt to haggle.
We usually haggle the same as real life. Usually this starts out with my players giving batshit numbers they pull out of their asses. I have them do a contested Charisma check against the vendor to see what the initial reaction to the bid is. If they fail the check it reduces the vendor's Morale.
Vendors want to spend low and sell high and generally know about how much an item is really worth, so they outright reject stupid offers, and they also don't want their time wasted, so they might get pissed if you yank them around (ever sold a car on Craigslist?). If the players make a reasonable offer the vendor usually takes it. If the players are being dicks I roll a Reaction check on the vendor to see if things get hostile. I haven't had players try to charm or intimidate any merchants yet.
Shop Quality
If a player wants to sell an item they have to find a place that buys things. If they think the thing is special they'll take it to a specialty dealer and see what they can get for it. Specialty dealers generally give a fair price (unless they're assholes) and if they're nice might even give a bit of backstory about a particular item.
Different shops are of different qualities. If my players ask about shops I pull d6 names out of my ass. A shitty antique dealer might be called something like "the Dingy Compass" and a fancy one "the Effluvient Gryffin". The players have to actually investigate the place and meet the vendor to see what it's like.
Fancy dealers want the good stuff. They can be stuffy nobles, shrewd businessmen, or eccentric collectors. If an item is worthless the PCs will generally be told so directly, possibly laughed out of the store. They'll pay handsomely for extremely rare or potent artifacts. If they're evil they might try to swindle the players by way underselling the value. It pays to get a second opinion, especially from a competitor.
Shitty dealers won't know much about an items backstory, but they'll generally buy anything. You might be able to sell a hunk of junk for more than it's worth if you're lucky, but probably you won't get top dollar.
The very bottom of the barrel is pawnshops. I don't have qualities for pawnshops, they're all the same. It's how my players unwanted stuff into coin. Don't bother haggling here, you know you're not getting a good deal.
This is for larger towns. You'd be lucky to find a general store in most villages.
Only Wizards can appraise the magical qualities of an item.
