Couldn't find any cost estimate, but from https://openquantumdesign.org/the-quantum-computer (scroll down to "What's Inside") I'm guessing 100's of k$ for the bill of materials (let alone keeping the thing going.)
So the "you" in "your own" has to have pretty deep pockets...for a relatively low fidelity 30 qubit device.
Most of the cost is in overpriced laser systems; if that gets solved a trapped-ion system could be reproduced for few tens of thousands of USDs. Still not a hobby weekend project, but certainly more attainable for more universities.
So the "you" in "your own" has to have pretty deep pockets...for a relatively low fidelity 30 qubit device.