Just to add to this, there's a reason why they are so expensive. First and most importantly, they don't make these in quantity like the DX4 heads. Obviously the more you make the cheaper it gets. There are a ton of printers using the DX4 head and that design is going on what.. 18 years?? The DX 5 is out only 6 or so and a printer uses one or 2 heads (I wouldn't count the JV5 as there aren't too many of these out there). Look at a Roland Soljet that uses 6 of these buggers. It must be over a 20 fold difference in quantity or more.
Secondly, There's not much competition. Whereas the DX4 heads have over 10 manufacturers, I only know of 3.
Thirdly, although it may be $2 of plastic injection, it's actually much more complicated than that. There are metal filters inside the manifolds. It's not a simple injection part and a multilayer process
Whatever the price, $80, $90, $125, etc. compare that to the DX4 manifolds at about $25... 2 Nozzle groups on the DX4 vs. 8 nozzle groups on the DX5.
It's hard to find people who want to part with their old heads. Everyone is keeping them for the manifold just in case the nipples break
It may seem like a lot but it's a hell of a lot cheaper than buying a new head. Lucky we even have replacement manifolds available.