Latency bounces all over.

I have an extremely fast Netgear Nighthawk CAX30 and the 1.2Gbps package and I get at best 800Mbps and most of the time like 400-500Mbps. This is absolutely ridiculous for the money I have to pay every month. I am hard wired for my PCs so I should be getting the 800Mbps at the very least on the regular. I am pretty sure Xfinity throttles customer's network speed.