AT&T and Sprint, for example, only includes 5G access in their two most expensive plans. Verizon offers 5G access on all its plans, but it charges an extra $10 for 5G. It's offering 5G access for free with its plans for a limited time at the time of writing.
T-Mobile is the only carrier that bundles in 5G access across all its plans, even its budget Metro-by-T-Mobile plans, without raising the cost.