I have never seen any side by side comprehensive evaluations of consumable life, but in general I think it is fair to say that you should buy a unit that is commensurate with your intended use. Not the the most expensive possible, nor the cheapest, but what makes the best sense in your situation.
I use a plasma unit a few hours a month typically, with some bursts where I need to use it 4-6 hours in a few days. I used to have a Miller Spectrum 375 which is a reasonably good plasma unit, but the torch was worn out again and had to be replaced again, so I decided to look around. I ended up buying an Everlast 70S amp cutter to replace it. The main reason that I didn't spend more is that I couldn't justify the business expense at this time. The Everlast unit happened to be on sale at Amazon for about $700, which was less than 1/2 what the Miller, Thermal Arc, and others I looked it.
It has a good bit more power than the Miller that it replaced did (roughly 2x) and cuts much faster. So far I see no difference in consumables. I don't doubt that one or two cutter/torch combinations by some premier makers wouldn't cost less to operate. I do know that with my level of use, I will be long dead and gone before I would come close to breaking even. The torch that came with my unit is a standard Trafimet S75 torch with consumables available from a number of sources. I would guess from my limited use (15 or so hours so far in 3 months), the consumables will last about the same as the Miller (needed none so far and have gotten high quality cuts in 1/4 - 1/2" steel).
So with a long warranty (5 years on the Everlast units) and reasonable consumable life, it works well for me. If I were using one several hours or more a day, my buying decision probably would have been different in that I would have bought one that was the most economical to operate.
To be clear here, I am not affiliated with any company and most of my welding equipment is Miller. That's why I bought a Miller cutter about 10 years ago, because it was the locally supported and 'safe' purchase to make. I paid what at the time seemed like a heck of a lot of money for it. When I started using it, I quickly realized that it made my OA torch obsolete for me.
Now that cutters are more common, supplies can be easily bought on the internet, and prices are more competitive than they have been in the past, the market has changed such that smaller shops and even home shops can have one. And there is a large variety of quality of machines from junk (imho Harbor Freight, LOTOS, etc.) to high quality units with a number of price points. Don't buy into the hype that there is only one good brand that should be bought in all circumstances.
Tom