$4/mo for 2000 minutes is reasonable. GitHub Actions does 2000 minutes for free/3000 minutes for $4, wonder if they'll drop their free tier a bit without the competition.
At $4/month you can get a server from anyone for 700+ hours of CICD .. this doesn't sound like a great deal to me unless you're CICD can't exist without ~2gb/ram and the cpu limits... Or unless GitLab runners have 16+GB RAM and lots of CPU for large jobs
Today, for our Linux Runners on GitLab.com, those Runners are currently offered only on one machine type, Google Compute n1-standard-1 instances with 3.75GB of RAM. Our current Windows Runners on GitLab.com are Google Compute n1-standard-2 instances with 2 vCPUs and 7.5GB RAM. In the future, for Linux and Windows Runners, we will offer more GCP machine types. For our soon to launch macOS Build Cloud beta, we are planning to start with one virtual machine size and then possibly offer different machine configurations at GA.
So as you get going initially with GitLab SaaS, you don't have to set up your Runners for your first CI/CD jobs. Then, depending on your requirements, and as your use cases evolve, you can easily set up your own Runners but still benefit from the included minutes.
CI/CD is mostly burstable workload. You are not going to run it 24/7, but when you need to build/test/deploy a commit, you'd prefer to do it as fast as possible.