Like Michele says, there has to be a reason. And those reasons are many, depending on several factors.
In your example, you use a Medicare patient getting a tonsillectomy, which "pays" at $1300.
Was there another higher RVU procedure done at the same time? That will reduce the payment for the second procedure.
Was the procedure done IP at hospital, or OP at ASC?
Does the provider doing the procedure participate with MIPS, or no?
Did the patient have deductible left to be met when procedure was done?
Those are just a few reasons off of the top of my head.