Insulated Doors

Hello all:

I’m looking to buy an insulated door for the garden-level door (under the stoop of my brownstone), as well as one for the door leading out to my garden. For two standard-sized fiber-glass Pella-made doors (that look like oak doors), I received an estimate of about $5,000 (includes installation). Anyone have another source?

Thanks.

P.S. Yes, I am going for the $1,500 tax credit.