It depends...
Zirconia crowns milled in China are quite cheap. No joke most low cost dental insurance crowns are now made in China
I don't do any insurance plans due to the nature of my practice. Crowns are not a mass produced product but are uniquely made for the particular dentist and as such the cost to the dentist will vary tremendously. The question that the dentist decides is how much time do I want the lab tech to spend on this patient's crown? His time and his material/equipment cost determines the lab costs. From the laboratory view they can only make a crown as good as the impression that the doctor gives them. In order to have a good impression the doctor must first have a nice smooth properly reduced preparation of this tooth. This takes time, quality instruments and high skill then after the doctor has done their preparation the tissue must be carefully handled so that the impression is clean and without any voids or irregularities. I prefer to digitally scan my preparation with a machine that is very accurate but costs 30,000$ USA again another cost.
As to your question the lab cost for a milled zirconia crown is much less than a high noble PFM. It seems your plan doesn't offer zirconia and therefore the "switch" so a much higher fee can be charged. A lab fee for zirconia might only be as low as 100$ or less.
Good luck