In my current campaign, magic items are pretty easy to come by. They keep those best suited for their characters and sell the others or donate them to increase renown with various factions. I use the Xanathar's Guide to Everything's downtime rules for buying/selling magic items. I am thinking of customizing the complication tables and rules, however, to both make complications more likely but to also have many more options, especially not particularly bad options, but flavorful and tied to my homebrew reputation rules. Complications would increase based on the frequency of selling magic items and other factors.
I'm running the game in Frog God Games's Lost Lands setting and use the city states for the limits on how much gold is available to make from selling items.
Even with a large amounts of gold that my players gain by plundering the megadungeon they are exploring, they have a hard time keeping the gold and selling magic items are one way to keep up with expenses. They have to spend gold on training to level up. They have strongholds, guards, servants, and followers to upkeep based on Matt Colevilles Strongholds & Followers rules. They have donations to make, bandit groups to pay for "protection", various grasping, petty Barons to bribe or pay off. There are taxes to be paid. Guilds to share the wealth with.
It sounds like a lot of work but I keep the rules pretty simple. I find reputation rules to be the best way to get them to sell gold and renown points lead to large dice to role on a table to obtain boons from various factions and infamy leads to troubles. More money, more problems.