The most expensive systems use continuous flow technology (also called binary array) to deliver ink. The print heads for these systems are costly, but they last longer than other types. The cost of ink, however, is very low. So you spend more now, but save over a long period of time.
Not only is the ink cheaper, it dries much faster than other systems. They also have a much longer throw distance (the distance that the print heads will "throw" ink onto the mail piece without sacrificing print quality). But of all systems, the print quality in general is lowest for these systems.
The less expensive system for bulk mail is the thermal inkjet system. You can navigate to https://camainks.com/ to get more info on mail inkjet systems.
The equipment itself is just as durable as the equipment used for continuous flow, but it costs less because it doesn't contain those high-priced print heads. Instead, the print head is located on the cartridge itself. So every time you add ink, you replace the entire print head. Unfortunately, that means the ink itself will cost more.
Despite that, many bulk mailers choose thermal jet systems simply because of the high quality. Thermal inkjet systems allow you to print unique graphics-ones that continuous flow systems will have trouble with.
At the same time, the throw distance for thermal inkjet systems is very short. You'll have to have the print heads very close to the mail pieces, which could cause jams in the line and hurt production.
The latest development in addressing equipment is the Domino L-Series Printer, which uses Lexmark technology. Technically, it is a thermal inkjet system, but it was developed specifically for bulk mail systems so a lot of the common problems were eliminated in its design.