I have only been buying APC UPS-Units for 30 years. While all but one (recent) one is non-Sinewave ... their approximation seems to be very good.
Even the small/inexpensive ones (around 500-size and no AVR) worked fine for ANY MAKE computer or home theater component I tried on it.
For the past 13 years, I've only been buying the black (upright) APC with LCD and AVR in the 1000-1500 range. In fact, I still have two working XS-1500's from 2010.
Since the price is about the same now, I finally tried/bought a UPS Pro 1350 Sinewave for my projector. Works fine. After 4 years, looks like it's battery-pack has gone bad (that is normal life).
Actually, I have 2 units down at the moment ... I think one just needs a battery-pack and the other is giving me a random "clamping error" (not sure what that one needs or if it's even repairable).
That link is from 2018. Did you read it fully? "Simple, every PSU that has 80+ certification has Active PFC." and other newer classifications. You require a PFC USP.
I am not sure what your definition is of 'cheap' either?
AVR's are generally cheaper than PFC's though, but not by a significant amount?
Depending on configuration, the size of the UPS does effect price. Also 'what' you want out of it? I've got an APC, 3 Cyberpower's, one being and AVR.
ALL perform the same, with the AVR not on a PC. Major differences, the APC offer up more than 2x the same size unit. Due to the cost of the APC and its battery size. The 2 Cyberpower PFC's are on 2 different XPS's, and one has more in it, in terms of a bigger (power draw) video card and monitor. This is what I get on my CP1000PFCLCD (Around $170 USD) depending where you buy it:
The estimated time will fluctuate as low as 35 minutes to as high as 50 minutes at idle. More than enough time to finish what I'm doing. The lower powered XPS will get over 64 minutes, and the large APC will do 1 1/2 hours. These are all approximate though and are usually less.
The bottom line is that PFC's are required. Maybe more expensive AVR units can produce the signal that a PFC PSU requires? I don't know? Not sure what you are calling 'cheap' UPS's either.
I guess it also depends on where you live if you might even need one? Having lived in Central TX which seemed to be the Thunderstorm Capital of the US, we'd have frequent small drops of the power during some storms. Now in Fl., the problem is hurricanes and high power usage (unusual cold and high temps) and power can drop for second or be out for a period of time with those nature events.
Cyberpower costs between an AVR and PFC unit is not significant to the cost of the unit with AVR being cheaper. The PFC 1000VA (600W) unit list for $180 USD and can be cheaper bought from stores. It is $70 more for the next size up, but probably could even double the uptime?
