Yes, of course, kilts are luxury item unless they are required for your work.

But so are nice shoes, suits, ties, etc. None of those things are absolutely required for existence.

I tend to think that fearing offense toward those who have less may be a bit condescending toward them. Not to offend you, but people are quite able to understand that folks who have jobs can afford more than those without jobs. Why not just wear the kilt (if you want to) with some fairly casual accoutrements, a plain sporran, shoes, and shirt or sweater.

A fur sporran or gold trinkets would be out of place--in my opinion--but simply weraing a kilt would not. Of course, I have also noticed that there are more basic yet subtle differences in thinking between the US and some parts of the UK. Maybe the kilt would be more offensive in Scotland.

I do know that in my own dealings with those who have a lot less--teaching, counseling, etc.--my kilt was never perceived as offensively ostentatious.