That’s a red flag in my opinion & would not use them for future jobs. Always ask for this or do not take on the job. You can do your own research on the material cost, & if they list their labor/time there’s no mystery bill you feel me.
Worst part was, this was the only plumbing company that would come out within 24 hours without paying the $200-$250 emegency show-up fee (which is an adder to the bill if you do it). I called over a dozen of them. I think there is some BS collusion going on.
I did talk him down to $500 when he got done which clearly shows this s#it is completely negotiable and he was still thrilled with his take. Also this was a plumber with a big, supposedly reputable, company, not an independent.