Couple of years back, I was discussing this issue with a friend. I'm very much a hobby user; he runs a small sign- and notice-board business. I built my machine from 3mm box section steel, all-welded including the gantry. Mix of 50x50 and 100x50. Cutting area about 1500x750. Components and material cost probably around £2-2.5K. Took around 6 months - but I'm not a fast worker. Now built, it works very nicely.

He wanted the machining capability as soon as possible, and bought from China (Acctek). He had done some research, spoke to them via Skype to sort out details, and very importantly found a UK shipping agent to handle all transport and customs issues, rather than pay China for carriage. That all worked out well, and he has been using the machine successfully. Their smallest machine, 900x600 (limited by available space), cost around £3K. It wasn't very well finished in terms of machining quality, paint finish, etc, but worked well after just a little bit of fettling. Little things like proximity switch target being out of adjustment - when we took the covers off to investigate, the "target" turned out to be a broken tap, screwed in the hole with a locknut. Worked fine after tweaking, but a bit rough! They do larger machines for, I believe, not that much more money.

I'm sure you could build better for less, but if you need the capacity now, what cost do you put on your own time? That's where home and business users differ. I'm sure this is exactly the kind of debate you are having with yourself anyway but if you have a sound business plan that needs this machine, you probably need to buy now rather than build. My friend has no regrets about going down that path - even if my machine is better than his!