I tend to only run shopping encounters if the PC's are in a new location that they are exploring. If the PC's have been around the block a time or to, there is no need to specifically run talking to Bob the Blacksmith unless doing so gives me an opportunity to impart some information.
I don't have magic marts, so there usually isn't a lot of shopping to do. When the PC wants some mundane equipment, just deduct the money and put the item on your character sheet.
Inventory management games should probably be mostly confined to single player cRPGs. Though I admit I'm struggling on how to balance that desire for speed of play with making finding loot as exciting as it was back in 1e days. Because, really, no system made loot more exciting than 1e. Loot was how you won.