In terms of costs your thresholds are the boiling points of nitrogen (77K, surprisingly cheap and easy to deal with, even for a hobbyist) and helium (33K, more

In terms of costs your thresholds are the boiling points of nitrogen (77K, surprisingly cheap and easy to deal with, even for a hobbyist) and helium (33K, more expensive,scarce, requires more energy to condense). To get lower than that, you need your own cryogenic cascade as I doubt you can easily buy something as ridiculously dangerous as liquid hydrogen (boiling point of 4K, explosive in contact with oxygen). At less than 2K I think that the only merits of this discovery are theoretical. I don't think that anyone believes that superconductors below nitrogen temperature have any viability outside the lab.