We bought the steam cleaner about twenty years ago, when we bought a used minivan that had some interesting stains, enough red Georgia clay to plant seeds in (front passenger floor mat), and smelled really nasty....it was the same price as getting the car interior detailed ONE time.
I was either pregnant or had a new baby and an older child - that machine has more than paid for itself over the last couple of decades. Several used vehicles were detailed - after we bought them or getting them ready to sell, flooded basement cleaned (twice), cleaned carpets when we moved out of a rental house (why put white carpet in a living room & dining room?), cleaned our new house when we moved in (it is also a tank vacuum and I happened to have it available - more than two cups of some kind of scented powder by the time I got the whole house vacuumed), and cleaned up coffee spills & more in the vehicles we owned (instead of having to have them detailed).
I like using it once a year or so on the family vehicle - more often if VorGuy manages to spill an entire travel mug of his morning coffee (I have no idea how he knocked it over and had the lid come off - but it took a while to steam clean that much coffee out of the carpet). I even helped a friend steam clean a used vehicle that they bought from a smoker....her dH (now her divorced ex-h) just didn't think about her being allergic to cigarette smoke when he bought the thing.....it took two cleanings to get the smell reduced enough that she could no longer smell the smoke (and half a day to dry out - we went out for lunch in my vehicle while her vehicle sat in the sunlight with the windows cracked open in my driveway - in the sunlight).
That was one gross tank of nicotine & tar as well as dust, dirt, and I don't know what else - the vehicle had belonged to a car rental company before they bought it in 2000 or so.
And - if you want something really gross - forget to dump the tank contents while various things GROW in the used cleaning solution - things that seem to be mold, possibly some kind of bacteria with a foul odor, and I'm not sure what else. I used BLEACH to clean the tank when I found that - after dumping the contents down the toilet and pouring bleach down the toilet, too.