It depends on server you're joining. If you're joining server closer your ping be low, but if joining server much more far example across the world, then your ping will be way higher.

The inconsistent can be due to vpn/proxy, DNS service, ISP, hops, pathways, and devices on either end meaning yours, compare to their server if it running on a toaster, or good device.

Also depends on where you are to the servers or if your system is clean.