I think it's interesting to also think about it from the other perspective. If this is someone who is supporting themselves through this work, then what they have to at least charge you is going to depend on how much they need to survive, i.e., buy housing, food, tools, etc. If they get only a few jobs per week, then they kinda have to try to pay their bills off of those jobs. They may also have a spouse, kids, and various others who depend on this income for survival.
Unfortunately, how much a person needs to have a decent living is not really what's driving prices: like all markets, what dictates prices is demand and supply. The job may be very easy for a tradesman to do, but if they're the only ones who know how to do the job, and many people need the job done and really can't just do it themselves, they can charge whatever people who need the job are willing to pay to not go without.
For most tradesmen , normally there are many "competitors", so they need to keep prices reasonable otherwise people won't hire them. Some jobs which can be easily DIY'd may just disappear as it's not possible to make a living off them, even if a small percentage of people will never DIY anything and would be willing to pay a small amount for the job to be done.
I am currently trying to hire builders for some larger projects at home (kitchen/bathroom renovations, custom car port) and I see wild differences in prices, and presumably quality. For these bigger jobs, it really becomes a bet unless you can actually verify the builder's previous jobs, which can be hard as people are not going to just let you into their houses to check how good/bad their bathrooms look. I've had bad experiences before, so I am being extra careful and trying to figure out the builder's level of expertise and capability by talking to them about lots of details (which I learned from previously building a garage).
what a person needs to make a decent living is an input into the supply part of supply and demand. Thus it puts a floor on prices. Pay me $500/hour and I'm installing washing machines not writing software thus increasing the supply of labor to do that. (but of course nobody will pay that much)
> If they get only a few jobs per week, then they kinda have to try to pay their bills off of those jobs.
I don't think this has been true anywhere for at least several decades. Every single tradesman I've used tells me they are overbooked/overworked and there's no shortage of jobs.
I'm sure they have their less-busy seasons, but overall I doubt any tradesman can't find 40 hours worth of work/week.
