Or, sometimes a combination of the two.
The setups for the DIY shops are usually fairly cheap IMO (Just looking at what's going on at them and the BOM) and the main thing outside of market saturation is having a good ingress/egress setup (If one sucks to get in and out of, folks won't come back.)
That's not to say that there aren't hand car washes as well, however I only tend to see those where I grew up (not too far from here, mind you,) or when it is some sort of school/church/etc fundraiser.
The weird thing you can run into in some cases, even at the automated shops though, is either weird 'implied consent' about extras by folks on one end or another of the line, or in the case of any of them, 'memberships' that are priced to where you'd really be following that 'one wash a week' rule to get your money's worth.
[0] - Often with a warning that they are not responsible for damage to vehicles older than X years and/or with more than Y miles
[1] - These can be surprisingly small, to the point some gas stations have one on the side and a purchase gives a 5/10c discount per gallon. Which, to the general point of 'pennies on the dollar' they made money on long term.
These big wash machines are typically staffed by only 2 or 3 people hence the complaints that they don't even create jobs.
That being said, I wish there were more automated washes near me. We find ourselves making excuses to drive by the one we pay a subscription for.
Reputable shops I more often see do something more like a 'Prepaid' discount where you get X washes (maybe in the next Y months) for Z dollars, and ideally it's something like you get one wash a month at a 10-20 percent discount.
The profit-gouging ones, either do a 'assume 3-4 washes a month to see real benefit' or assume you are washing once a week in their sub... or do all the other 'tricks' above schemes can allow.
But I never see anyone using the subscription car wash in town, so who knows? The new ones connected to the gas station see some action.
As an aside, the entire experience is awful. "Pay $25/month and get as many $8 washes as you want!" ...but I only get a car wash every 2 months and since you're tracking my license plate, you already know that.
>They're legit
It is hard to know whethr they are working legally.
No?
Most casual work was done by teens and middle aged women through history but now it's mostly foreigners.
Anything done by citizens attracts huge markups.
I expect the main difference between the US and UK versions are that the latter are typically set up in disused urban plots with pop-up tents and temporary chain-link fences rather than having any investment.
Either way, if you're getting 3-5 people washing your car for a tenner, the people you're handing you money to are probably receiving minimal pennies on the dollar.