CI pricing (gitlab, github actions, circleci etc.) is all extortionate. When they price by 'user seat' (gitlab) or 'credit' (circleci), comparing pricing is like trying to pick a cell phone plan. AWS Code Build will always be an order of magnitude cheaper, it's just slightly harder to set up but it works very well. It's unclear how all these other services will ever compete with that. For example, to run a CI server…
If you’re using a dedicated ec2 instance, most providers (gitlab, buildkite, github, etc) will let you connect it as an agent for free.
IMO using your own runner is a better way to go in general because the standard ones tend to be very underpowered and you can get much faster builds without spending much.
At that point different providers are largely competing on price and UX (imo Buildkite have the best developer UX and the time saved as a result is well worth the price).
(Not affiliated with buildkite other than as a user).