A while back I've seen the DPS5015, which is a 50v 15A programmable power supply which has other versions, 30v/50v, 2A/3A/5A/12A and 15A, add on top of it the possibility to DIY your own programming and it looks like a winner to me (~$37).
You can even get an enclosure with a fan for it (~$24).
But that is just the controller, it needs a power source of some sort, I've looked around and found a 48v 16.7A switching power supply (~$73).
Throw in a couple of banana screw terminals ($1-2) - don't get the cheap ones, they fall apart.
and add a 3 Terminal Power Socket with Fuse Holder and you have a working power supply (don't forget the fuse! I've used 5A)
A few wires and a cover for the power supply and you're done.
For now, the only drawback I've seen is that this specific PSU doesn't monitor the temperature and power the fan accordingly, so the fan is always on, making a lot of noise.
I've thought about adding something like this to fix that, but I'm not sure yet, need to do a bit more reading about it and see if the power supply needs an always on cooling or not.
In the end, the time and effort to find the parts, read, design a back cover, print it and build it took a long time and I'm not really sure its efficient use of one's time, but I've had fun doing it!