[RPG] What’s the starting wealth for higher levels

The suggestion I'd make on handling parties that use an abnormal amount of consumables is the one of staying true to what little rules we do have: hand out an appropriate amount of treasure, and let the players decide how to apply it. If they spend lots of gold on consumables, they end up with fewer permanent magic items. If they spend little... well, they'll have more shinies. In other words, I do not suggest enforcing WBL on characters that already exist - and there is no rules premise for doing so, as far as I can tell. What you should be focusing on is handing out the correct amount of treasure.

Starwed's answer contains information on how much gold the game assumes characters will collect throughout their adventuring career.

Nope. Guidelines for how wealthy or magic-powered PCs were didn't really become important until 3e introduced a system that cared about balance enough to need official guidelines. In 2e, everyone just winged it and it worked fine.

Your provisional rule is pretty much how it was always done: pick some numbers, play! The actual numbers picked are pretty much a matter of taste, reflecting how much or how little magic and money you want to be laying around at the start. Go for it!