It's a small but important market. People who need HPC generally really need it, and despite other comments no, you generally can't just rent time from some cloud provider: a huge farm of machines is not an HPC system (even though HPC systems are huge farms of machines, they also have serious interconnect & I/O), and while there are a few rent-HPC-time people a lot of HPC users are understandably uncomfortable about their code running on other people's machines.
Unfortunately because it's small, relies on a tiny number of very large purchases, and is dependent on governments, it tends to be very variable. HPC makers have the some of the same problems that very expensive car makers have.
[source: I run code on HPCs.]