What's the real world connection speed from your residential IP to your Server?

I'm using contabo and the VPS I got is advertised as 1 Gigabit. When I do a speedtest or use iperf3 to connect to public servers I get pretty close to 1 Gigabit. But from my residential IP the speed drops down to 100-250 Mbit/s. My home internet connection can handle 500 Mbit just fine....