If your neighbor has a faster speed package, he will get slightly higher speeds. If you're doing a test there...the best test is to take your own modem and actual coax cables and ethernet cables to test it there...however, that's annoying cause you may have to call Cox and provision a new MAC and serial number for your modem on your neighbor's account.
I have Gigablast and have been barely getting a third of the speeds. I've had the same issues at the Cox box (demarcation point) where my speeds are bad...even after a Cox tech re-wired some stuff. I hooked up my own new coax to the Cox box and got the same bad speeds.
Cox's tech meters don't seem to go through the same "traffic pattern" as customers do. It's similar to speedtests on NETGEARs Apps which will almost always show faster speeds than you're getting. Their meters also seem to have a dedicated "server" to them back at a Cox main office in the area. Additionally- I've learned that the Speedtests appear to be measuring how "fast" you can touch the internet, but not the responsiveness of actually accessing and using the internet.