I'm not sure how many they've actually sold but i do know that they have a loan/test program where you can pay a relatively small amount (around $2000 or less) to get set up with a MinION kit. The main recurring cost is the flow cell. I'm currently trying to figure out how to join together short multiplexed samples (150bp - 200bp) and get it sequenced on the MinION. Current short-read sequencers from Illumina or ThermoFisher cost orders of magnitude more than Oxford Nanopore's offering. Hopefully someone else is trying to use the platform for short reads.

I got mine as part of the beta almost two years ago. It's been in release since, and seems popular in the community. It's not Illumina HiSeq popular, but the cost is low enough that lots of people are experimenting with it.

Nanopore sequencing is definitely "already here" in the sense that they're selling a lot of flow cells and people are doing useful research with ONT instruments but it's also a niche technology compared with Illumina.