You find that many places post these amazing Speedtest scores. There was some ISP in Riga (Latvia) that was showing extremely high results... However when you do some more extensive testing it doesn't seem to bear out. So why is that? Well because they run their own Speedtest server and operate their stuff like a big WAN.
It is not so hard to provide a big link internal to your network. It is a lot harder (meaning more expensive) to provide enough backhaul to make it fast to the majority of the world.
I mean I can truthfully say I have a gig here at work. I can do a Speedtest to show it... to the Speedtest server in our datacenter down the hall. Off campus I still see good connection speeds, but nowhere near a gig, as we have only about a gig of bandwidth for the whole campus.
Most US ISPs don't offer big links to customer houses, but they do tend to keep oversubscription manageable so you usually get around your rated bandwidth. What you find is that places that offer off the charts Internet speeds for cheap prices are doing WAN like setups and there isn't the backhaul to support it.