I want to buy a standing drill press.

[House of Roberts]

13. So regular 118 degree (or 135 degree) drill bit? With TiN coating, that's gonna be pricey,

but so is anything 1.75" diameter.
I'm trying to think of an alternative tool that could work, like a hole saw with the right diameter for the tubing to seat into the 2x4, but it might need to cut a thicker groove than the standard hole saw to work.

I could see using one 2x4 with holes through as a template to spot your locations on each regular 2x4, then you wouldn't have to lay them out individually. You'd still have a lot of holes to drill, but it could be repeatable and make your top and bottom sections more likely to match up. You'd need your depth of cut to be consistent, but that's why you'd use a drill press and not a hand drill.

I hope you can work out the kinks in your process to make it efficient. And find a reasonable priced drill press.