You know I haven’t gone back through the bill of materials in so long on HercuLien. A lot of the sites in my bill of materials are not updated links anymore. In fact I think I used the Google URL shortener for several of them to try and make the links not so long and I’m not sure that Google URL shortener even works anymore. But unfortunately I don’t think you’d be able to build HercuLien inside that budget range unless you are really crafty. Also I designed it so long ago that there are many things that I would probably change on it if I went and redesigned it from scratch now. I’d probably do an active three lead screw leveling instead of two leads with a belt coupling. Ideally you’d use 3-point leveling and a contact probe (three points define a plane). Because even the most stable kinematic mount with cast plate is subject to different thermal expansion at different heat bed temperatures. So a contact base probe takes care of that, and allows you to switch bed materials from PEI spring steel to glass etc depending upon the filament that’s going to be used. Something like the Railcore or Muldex setup.
The other tricky thing about a crossrod gantry like Ultimaker, HercuLien, and Eustathios is since several of the rods act for both rotation and translation, it requires bushings not bearings. So the stack tolerance of the entire gantry can be problematic for some. I’ve never had a problem getting alignment, but that was probably the single biggest thing I had to provide support for on my design back in the Google+ days. You have to have pretty exacting assembly, printed parts, and frame fitment otherwise you’ll run into binding issues.
Currently the printer that has me the most excited is the Muldex. The design and attention to detail is just amazing, and having dual independent extruder on corexy is quite an accomplishment. That’s not to say coreXY doesn’t have potential issues. Differences in belt tightening, frame squareness, etc can cause issues with circles being more like squircles.
This is a bit long and rambling, But what I will say is that every time I tried to build a printer for cheaper than a kit, I ended up losing that battle. I’ve designed many printers over the years now and never has my self-sourced one ever been a cost savings. But each printer I designed was for a specific purpose and I think normally I fulfilled that goal because I could make each printer do exactly the things that I wanted to knowing the limitations of each style of design. Every printer design is good at some things and worse at others.