How much should a person spend to get a decent power conditioner?

Well the ideal of perfectly designed components, cables, and reliable clean power is mostly a pipe dream....

to wit I bet you will find many a dirty wall watt switching supply in many many systems

most people have at minimum a network switch nearby and the wall wart to power it.

most servers, DACA, etc lack a properly designed Faraday cage to keep the analog side clean...

so gathering all your dirty dirty stuff up into a low end $500 Furman or similar and putting that on a dedicated circuit will do wonders for your and most any system

i have all three of my systems wired this way, two w Furman, one Isotek

In my experience, probably 2g is my cap

the right one does make an audible difference

Btw
bought both Furman for less than $250....each
they are out there....

I recently purchased a Furhman M-8Dx merit series power conditioner, 15 amps with 8 rear plugs and one front plug.  It has two lights in front that telescope out to illuminate components under it.  I had a low level hum in my system that I was hoping it would address.  It did not.  In fact I agree with the previous comments that the primary noise issues come from specific components, even placement relative to each other.  In spite of the non resolution of the hum I mentioned, I love this unit.  It looks nice, and the sheer convenience of having all my components plugged into one main power switch is nice.  I like the lighting.  I like how it looks, it has a power read out.  Does nothing for me, but tells me how much the power company in fact varies in voltage.  Its a lot!  I most like the phsychological idea that it provides a layer of surge protection.  It also spaces the plugs on the back so you can fit wall warts easily side by side if needed.  It was just over $125!  Not 4 figures.  It is rack mountable.  I have mostly tube powered amps and pre.  I find the tube selection makes the most impact on the noise floor.  The only other noise problem I have is related, of all things, to my I-Pad.  After buying a new RPM 9.2 turntable with a Sumico EVO II cartridge, I found the system was picking up my I-pads communication.  It sounds like the old Sputnik satellite telemetry, beep, beep, bop digitized pure tones.  Maddening. I thought my phono section was bad, it wasn’t.  When I put it in airplane mode the noise goes absolutely away.  Maddening because I source Spotify Premium which is better than CD quality.  The rest is vinyl.  I’m told now I need to change the tone arm wiring to a shielded variety.  I guess we will try that.  Back to the Furhman, I really like it but because of the conveniences and surge protection.  I installed a second ground outside on my electrical system to see if that also helps.  Deep copper rod into the ground.  I also have copper pipes in the new home vs. vinyl, and they connect to my drilled well at 170’ deep so I think I’ve got that covered.

Brick wall Audio competed well  against units $1500,at
under $300 ,buy the Audiophile model.   Class -B  2 years ago Stereophile magazine.  Very solid and nothing close at this price point.