My experience has been they insist on paying their GSA schedule price, which generally is below list.

It’s below list, but every procurer on earth knows that, so it’s above the price private companies pay.

When I was in product management, GSA price lists were my trick to learn what competitors charged.

Isn't it an easy way to get blacklisted if you sell to private companies below the GSA price? At least that seems to be the predominant assumption most scientific equipment companies operate under.

I don't know, maybe that is a thing, and maybe things have changed, but when I was doing product pricing, our assumption was that the GSA price was going to be somewhat higher than the "discounted" price most customers would pay.

The common trick to change the product, such that it is different is some non-fundamental way. Then it isn't the "same" product.