There are still people building legitimate cabinets but few want to pay what it really costs to build them.
To even get apprentice type wages on building a complete machine including all parts, materials, artwork, etc. puts a regular upright into the realm of $4k+ depending on all the details.
And sure it will play games but no matter what parts you change on it, an Arcade 1Up will never be a good long term investment in a gaming machine.
A properly made one will survive decades of regular use.
I built multi machines that have been in a surf shop and pizza parlor in my town for 5 years and counting and I haven't had to perform a single bit of maintenance on either.
No modded 1Up would have lasted so long.
Where do you live?
You DO need to be careful about custom builders though as there are a few guys building what look like ok machines but they are cutting corners on process, over-charging for materials, and offer terrible service overall.