This is not very realistic. Recordable and rewritable Blu-ray Discs are a much more consumer/prosumer-friendly backup solution, and yet, due to low demand, the market is slowly dying. The market size for prosumer tape drives would probably be even several times smaller.

The market is tiny and already served by surplus enterprise gear

Maybe if this 5x production ramp up finds that the demand wasn't there long term we will have a prosumer line after all.

Because the entire market would be a few thousand people.

Maybe that ship has sailed? Used to be a thing, but now people rely on cloud backup and assume they are doing the right thing.

Tape drives are really picky compared to HDDs: they don't like it when the environment is too hot, or too cold, or too humid, or too dry, or too dusty, or with too many vibrations, etc. They're really only meant for datacenters with controlled environments. A prosumer version would need additional engineering for environmental tolerance that the enterprise ones don't have, and end up costing more, not less, especially with the tiny markets involved.