But it seems like as soon as one Rich wealth level PC joins the group, it's irrelevent that nobody else is rich. I mean, the rich guy can supply every other PC with anything they need.

Perhaps in your campaigns this isn't a consideration, but I find it peculiar to have wealth levels at all if even one PC is 'rich'. Does anyone use some sort of generic Difficulty scale to see if items are available to rich folk? I'm sure weapons and equipment would be a snap for a rich character, but what about buying a yacht with a bathesphere? Can they get one of these on the spur of the moment just because they're rich? How rich does one need to be to find a bathephere-ready yacht for sale within 3 hours?

So, does everyone just wing it, or do you allow anything at all to be available to rich PCs, or what?

Curiously,
- C

Poor - 1 vehicle of your wealth level.
Working Stiff - 2 vehicles of your wealth level or lower.
Rich - 3 vehicles of any wealth level.

You could make it so that wealth levels can change. If a character is continually using their wealth to fund the party, you could warn them that they're starting to run low on funds, and risk becoming a working stiff. Similarly, if a character puts a lot of effort into accumulating wealth (in ways that don't hold up the action) you could gift them an upgrade.

If a plyer group wind up owning a shop (like the Eating Counter from Baptism of Fire) you might want to make poor characters effectively working stiff (as they get some money from the shop and they never have to buy food for themselves).