The Linton contra clarinet is in Eb, so you'll only be able to get a Bb contra by calling up Orsi and asking them to make you one
. Also note that the Linton's mouthpiece is not standard size.
When I check ebay for horns, if I find something interesting, I try to post it here. I list some Sarrusophones
in this thread. I've listed a bunch of things, including F Mezzos,
in this thread. Quinn the Eskimo (I should get paid more for mentioning him all the time) has had all of the horns you mention at one time or another, with maybe the exception of the Linton and contrabass sax, as has Paul Maslin, as saxhound mentioned.
Being realistic with your list, it's *possible* that you'll find an F Mezzo or the Linton contralto in the $3000 range. I can't remember a time I've seen bass saxophones in the below $6K range.
New Soprillos are currently in the close to $4000 range and I think I've only seen maybe one or two used ones out there since they were introduced. You can look at the threads I mentioned and find an average price for some other things on your list in the $5K+ range.
You didn't mention Rothophones. You need several in your collection
.
I also suppose it's possible that someone has a big, hulking contrabass saxophone in their attic and hasn't bothered trying to find out a value for it, but most people know that there's such a thing as ebay. It could happen. Hey, I'm writing this sentence using a 1994 IBM Model M keyboard that I bought for relatively cheap and I've fixed it up to look pretty much brand new. In this condition, it's worth appx. three times what I paid for it -- although it's nice enough that I might keep it
.
I wish you luck. If you do have a decent paying job and you're still working throughout this coronavirus stuff, it's a buyer's market.