I don't think there's a universal answer, I think it depends on the goal of the equipment list.
Many SF games have exhaustive equipment lists, full of all sort of high-tech goodies. So behind the curtain is that credits (or whatever they call their money) is a stealth part of character advancement math and you can get a lot of cool stuff.
D&D 4e is the same way, if you combine the mundane equipment and magic item lists.
D&D 5e on the other hand does not default that way - magic items have no price, so gold is for mundane equipment, and outside armor improvements the first few levels is not a part of the math of character advancement - it doesn't change numbers on your character sheet.
Spy games are usually full of various gadgets and stuff, but they are also usually based somewhere near realism so you need to have a wiretap to use it, etc. But sometimes they have an interesting relationship with money, for instance the (80s?) James Bond 007 game had all sorts of things from the Q branch, but you couldn't buy them, just get assigned them. So they were temporary superpower boons the GM would hand out for the current assignment.
On the other hand you have games like Blades in the Dark, where as part of it's "we've already planned" conceit you only say if you are bringing a light, normal or heavy load, and equipment is with you in a undefined state until you use it. Basically, it's the flashback equivalent of stocking for a heist. But the equipment available in the first place is mostly dependent on your playbook, there are no generic equipment lists.