The perpetual quandrary
With an instrument like the bassoon, any that are "good" (in the relative sense of the term) are likely to be spoken for before they go on sale. You may occasionally come up with a "good" instrument (rather than an average one), but it's going to be a matter of pot luck if you blunder into it.
The fact that you posted on here indicates to me that bassoon playing is not your primary interest. Unless you play a lot and have the chops to make it work for you, a "good" bassoon is going to be price overkill. It's not that you wouldn't appreciate it, just that it's going to be many orders of magnitude harder to find that "good" horn in a sea of average and student ones.
If I had my druthers, I'd opt for a polypropylene instrument, simply because it's many times more stable and immune to wood issues that will be present with a wood instrument. (It would help with the price a bit, but not much.) If nothing else, a plastic horn will have fewer potential abuse issues, simply because of the body materials.
And, I'd set my mind at being ready to pay in the neighborhood of $5,000 for that "good" instrument (and maybe not finding one at that price). Push comes to shove, you are purchasing a horn that involves more in the way of finishing than does a clarinet or saxophone. Work equals labor costs, and labor costs equal a higher price.
As for specifying which optional keywork you'd like to have, every such addition to the specification makes it that much harder to find something that will fit the bill. Nothing wrong with having a row of keys there that look like the buttons on one of Marlene Dietrich's long slinky dresses, but the more customized the arrangement, the fewer there will be to pick from in the final analysis.
This would all be simple if only you would agree to take up the harmonica...
