I managed to get two of those PSUs for $3 each from the Arrow Electronics sale. Partly to mod one into an auxiliary power supply for solar applications, partly to understand how such high voltage PSUs are designed.
To open it up, remove 4 screws on the back (heatsink), then wiggle the cover free of the terminals.

I'm surprised to see a huge empty space inside (maybe the case is shared with a higher power version?) and even more surprised to see the high voltage transistors attached to the heatsink with only a thin silicone pad in between. I recall a teardown of a different high voltage PSU using much thicker ceramic slabs for coupling the transistors to the heatsink.

The HV board, oddly enough, has the fuse on the output of the bridge rectifier. That I don't understand, it means a short in the rectifier itself would not be protected against (which would make quite a fireworks show on a 480V supply!) and the fuse would have to be rated to break DC current. (The three black things on the input are ferrite beads for EMI.) The high voltage transistors are FQA11N90 in a full bridge configuration, which at 900V rating doesn't leave much margin at the claimed 575V maximum input rating, especially with no snubbers. The thing in the middle that looks like an iron core transformer is a choke for passive PFC.
A UCC3808A-1 is the controller with a 4060 dithering the switching frequency.

The LV board is about what you would expect, transformer, rectifier, output filter, and feedback. The rectifiers are DSSK60-015A in center tap configuration.