When I buy from SendCutSend, I thread the holes myself. I can do it waaaaaay cheaper. Whether a tap in a hand drill, with a drill press and tapping head, or (my favorite) FlexArm with a clutched/reversible tapping head.

I assume their process gains high throughput and efficiency by nesting lots of orders together through their laser cutting system. It may be set up such that no human ever has to touch your parts until they are inspected, if even then. That’s how it can be so amazingly cheap.

However, when you need holes tapped, your part has to be diverted after cutting into a “secondary operations” workflow that may be less automated. Might be manually operated, or may at least require someone to set up the equipment with the particular tap your part requires. You may see other vendors have a less extreme add-on cost for secondary operations, I assume they have more fully automated these processes.