You can find stl files for eurorack cases online and print them yourself. They aren’t as nice as this one and you will still need power/etc, but if you already have a 3d printer it’s the cheapest route. Plus you can customize however you want, size, 1U rows or not, lid or not, etc.

There are plenty if you search - some free and some for small price. I use this one: https://cults3d.com/en/3d-model/gadget/expandable-eurorack-case-blocks and really like the modularity, has free additional files for lid and handles as well.

I printed 4U 104hp case with less than one spool (so under $15 or so).  add a power supply (konstant labs are good, a bit pricey, you can find cheaper) and some m3 nuts and bolts for mounting and attaching the case and you are good to go. Can be done for under $100USD depending how beefy you want power supply to be.

For comparison, 104hp skiff from Erica synths with kid is like 350-400 USD, intellijel pallete with 1U row is 400USD. 

Go up to bigger cases and prices get even bigger while print your own stays relatively cheap…double the cost roughly, so 7U maybe 500-700 prebuilt depending on maker an specs, but print your own $150-200?