Is $4,000 to install a 3-panel custom glass shower enclosure with a hinged door a fair price?

I need custom shower doors for my new shower. I was quoted $4000 for a 3-panel glass enclosure with a hinge door in the middle, which feels really expensive. I'm looking for cheaper online retailers. For my guest bath, I found premade options online, but my current shower has a bench on one side and a half wall on the other, so premade options won't work. The contractor refused to give quotes without the bathroom being tiled and grouted. The shower doors were included in my rehab loan contract, which allocated $30,000 for the master bath. I had to get a quote signed within 2 weeks and didn't have time to itemize everything or pick out all finishings. My contractor quoted a basic master bath with large format tiles, but I picked smaller tiles, leading to a change order. With all my chosen finishings, we are already $15-20k over budget, which I approved. I need to talk to him about the shower door but am trying to find cheaper options first. The bathroom is huge, around 200 sq ft. I was startled by the price and just want to make sure I'm not getting ripped off. I would have been very upset if the bathroom didn't turn out this good because it was not cheap.