Instead of spending a lot of money, why not do like I have for years
and wear some soft foam earplugs under the headset?

Not a bad idea, but I'm more concerned about the comfort (i.e.
vise-like pressure on my head) after about an hour or so. The gel seals
help a bit but I understand typical passive noise reduction headsets
are all pretty much the same as far as clamping pressure(?)