He explained that shifting from more smaller screens meant that he could remove the bezel from right in front of his face. Those big, curved screens are brilliant to use IMO. He might have passive income from Pluralsight courses, have his mortgage paid off and figure he might as well use the surplus cash to treat himself. Others might spend more than that upgrading a car they're suddenly using less than ever before.
An honest setup could be had for much less. I think he could save quite a bit on his PC with custom built, screens by going smaller and more numerous, camera by going 1080p instead of 4k. That would be a perfectly good work from home setup but he wanted to go max and blog about it.
but tbh from the invoices i have seen for business 'expenses', 10k for a critical part of your work flow is forgiveable.