> It's somebody else who owns much hiqher quality printers that you would buy,…
This is just completely untrue. What kind of machines do you think they have back there?
Photo labs typically have two types of machines: something like a Noritsu which prints onto standard RA-4 paper with lasers, and ordinary inkjet printers, like the ones from Epson or Canon (like what I’ve purchased for myself—I’ve occasionally seen the same exact model behind the counter at photo labs—the same printer I have at home).
The advantage of the Noritsu style machines is that you can churn out hundreds of 4"x6" photos per hour. It’s not higher-quality than inkjet… actually, inkjet prints are better, and you can do that at home. If you think about it, it makes a lot of sense—the Noritsu is constrained by RA-4 chemistry, but the Epson / Canon ink can be anything that you can squirt out an inkjet head.
You can calculate the break even point for inkjet printers. If you’re printing, say, 8x10s, then break-even is somewhere around 200 prints, over the lifetime of the printer, compared to using the cheapest discount services online. This is if you decide to get a photo inkjet printer (around $300), account for the cost of ink ($0.01 per square inch) and high-quality paper (also around $0.01 per square inch) and compare it against online services (around $3 for the cheapest 8x10s).
If you aren’t printing many photos or are sticking to the super-cheap 4"x6" size, go ahead and take your photos to the lab. But the photo lab ain’t magic—it’s mostly just equipment that you could reasonably buy for your home.
It's somebody else who owns much hiqher quality printers that you would buy, and who charges everybody for a markup (so it gets spread).
It's usually cheaper to print in such a service than to buy printer+ink+paper and print - and with better results.