I collected a few over the years. It was the instrument I spent time on before I got into ukuleles some eight years ago. Except one, they are all Hugh Tracey / AMI kalimbas: a 15-note G-tuned one (with soundbox), three chromatic kalimbas with tines on both sides (two with sound boxes, one without - was an oversight I ended up with two identical ones), one treble kalimba with 17 notes, three karimba models (one in Lotus tuning, another in a minor tuning, and one in an African tuning with little brass rings). I also got one of the Chinese 17-note models in C tuning that have been around for a few years, by Gecko (found it disappointingly quiet compared to the Hugh Tracey ones, but it was also substantially less expensive). Oh, and I have a Sansula Deluxe, with just 9 notes, but with a beautiful sound (but I feel it was too expensive and too much of a one-trick pony).
I have been meaning to sell most of these, but since they take up little space, I still have them all. I acquired them over the span of years, not all at once.

Also went over board with ukuleles and then trimmed the heard. Luckily with banjos this has not happened! Only have one of those with a second one being built - no plans for more. No, really.

They are not very collectible, just too large and expensive.