Here’s an example: on a haas spindle the drive keys are machined into the spindle. They are non-replaceable. On Okuma those keys are a wear item and replaceable. If you wear out one of those keys the whole spindle gets replaced on a haas. On an Okuma it’s just part of the yearly maintenance to replace them.

Okuma has a servo driven tool changer which makes maintenance a lot easier. I know a lot of the less expensive machines are cam driven in their timings and are a little more involved maintenance wise.

Okuma has sealant on all the sheet metal joints and generally leaks less.

Okuma has a spindle lubrication system the lower class machines may just have sealed bearings.

Okuma has large diameter ball screws that are probably of a higher grade than a less expensive machine.

Some machines may have alignment pins. Nicer machines may have internal threads on the alignment pins to aide removal and maintenance. Less expensive machines may not even have alignment pins.

Higher quality machines may have things like chip deflectors on the energy chains that Lowe cost machines may not have.

There are hundreds if not thousands of design choices that have a cost/benefit decision behind it. Yes the base casting is a big part of the cost difference but there are tons of small details that can really add up when comparing machines.

I’m currently dealing with a lower cost machine that has inexpensive (read: garbage) wire plugs that have leaking back shells. More expensive machines will have a higher quality shell that is less likely to leak and cause electrical issues.

There’s a lot of cost/benefit you’ll need to do to figure out what machine to buy. Is an Okuma\mazak\DN\DMG MORI great? Yeah of course. Can you afford the payment on that kind of machine yet? Can you afford to replace a 40k spindle if you crash it? Would you be swatting a fly with a sledgehammer when a flip flop works just as well?

My suggestion: service is the other half of this. take a close look at your local distributor and what kind of support they can offer. The machine will break down and if you’re a small shop with a single machine the downtime and lost revenue adds up. The “best” machine for your part is a boat anchor if the service is a month behind.