This. I used to colo lots of stuff, but now mostly use Hetzner. But there are many in this space, and some of them even offer an API. And some of them (like Hetzner) also offer at least basic cloud services, so you can mix and match (which allows for even steeper cost cuts - instead of loading your dedicated hardware to 60% or whatever you're comfortable with to have headroom, you can load it higher and scale into their cloud offering to handle spikes).

The boundary where colo and dedicated server offerings intersect in price tend to be down to land and power costs - Hetzner finally became the cheaper option for me as London land values skyrocketed relative to their locations in Germany, and colo prices with them. (We could have looked at coko somewhere remote, but the savings would've been too low to be worth it)