
I’ve been through that same merry-go-round circular thought process.
I do wish there were more affordable MPE options, but there are more options now, and at lower costs, than when I started.
The Roli Lightblock M is probably the most affordable at the moment. I haven’t tried one. The first gen lightblocks were pretty universally hated as being unexpressive, but the M iteration purportedly made the surface much more responsive, and I have heard some positive reviews. It also uses an isomorphic grid layout, which I feel is more amenable to microtonal/non-12-TET music than any piano-esque layout.
If you can spring for a Linnstrument eventually, I highly recommend it. I absolutely love my Linnstrument and expect to be learning more about how to play it for years to come. The only instrument that tempts me to move on is the Haken Continuum, but I may never feel that flush.
There are other affordable options I have given less thought to. Joué, Artiphon, K-Board Pro, are all options. I wonder if there are others? I also wonder who’s going to be the first to come up with an affordable DIY approach…