A lot of their writing gets done by people making less than them, like legal aids. I've written content for lawyer's websites for not much money.

I also wrote legal notices as part of my corporate job. I started at like $9/hr and was make $12-something/he when I left.

Some letters got reviewed by the legal department and approved by my boss, but I wrote them (using a form letter to get me started, then fill in the specifics).