The only downside to dot matrix is the noise and low resolution - otherwise they are extremely reliable, high-throughput printers that are still used extensively in various industrial and other niche environments. The ability to print lines or even individual characters as the data comes in and use continuous feed paper is not possible with inkjets or lasers.
Operating costs are relatively low but they are definitely NOT cheap to purchase.
Occasionally, you can find one on craigslist or at a yard sale for a couple of bucks. They're pretty much indestructable, and printer ribbons can be found online.
I used to work as a service rep at an airline. We used these things extensively for printing airline tickets. These tickets had four red carbon-copy type pages that needed to be printed at once, and a dot-matrix printer is the only thing that handeled this well. It was a small office and we had just a rickety old Star Gemini II printer, but I must have printed thousands of tickets with it before it was decomissioned when e-tickets made their entrance.
I'm seeing, like, $160 for a consumer BW laser and $330 for a dot matrix. Considering the BW laser will probably die inside four years for no good reason, and refills will be about $60, the dot matrix doesn't strike me as expensive if it will last.
Operating costs are relatively low but they are definitely NOT cheap to purchase.