The price list link at the top works, but the one at the bottom doesn't.
Basically, a new 2-way door like that runs US$1400+
You're not spending US$100, you're saving US$1300!
You're not putting in a big ugly contraption, you're making yourself more available to your family when you're dark in the darkroom, and permitting them to share your darkroom more with you!
(*diabolical laughter*) Bwahahahahahahaha