You could cut down two 36" doors. You need a table saw to get a perfect cut.

There are handymen and carpenters who may see your question and offer a more authoritative answer than I can (I build furniture) but it doesn't sound exorbitant. I don't know what the door "system" itself costs, but installation labor can vary widely depending on where you live. You won't know for sure whether it's reasonable unless you get multiple quotes.

The ones I got for my library open from the center and swing out, not into the library. My parents have french pocket doors between their kitchen/dining and living room (that are always open) and set of traditional swing open french doors between the dining area and their smaller sitting area off the kitchen which they keep closed during the winter since it gets less use then. Mine were purchased through my builder, they are solid wood like the rest of my interior doors. I believe we got them from Western Door. Western Interior Doors

Use a brush type door sweep.