DIY since I retired. Can't afford a $250,000 table, but I can get the same or better performance with a little thought and lots of research. All it takes is time, that and willingness to compromise on non-essentials. So my table doesn't have a pretty chassis machined from one piece of stainless, but it does have air in three dimensions for contactless motion, which puts it in rarified company.
So buy off-the shelf when you can, make it when you can't, and contract out when you would need a 15" lathe. And search those surplus sites - you never know when you're going to need a 25,000 pF vacuum cap or two (works wonders, wonders in my RIAA).