When I download a large file on LTE (Verizon) I get between 2MB/s and 3.5MB/s transfer rate, through it will momentarily go above or drop below those rates.
1 byte = 8 bits so:
2MB/s equals about 16mbps and 3.5MB/s equals about 28mbps
If I test my connection on speedtest.net guess what? It shows between 16mbps and 28mbps, sometimes spikes to 30mbps. I've always found speedtest.net to be accurate and correspond well to real world tests.
Now if we're talking simply browsing, most people probably couldn't tell the difference between 50mb/s and 1000mb/s (assuming latency is similar) because most websites just don't need that kind of speed to load. Does that mean the 1gb/s connection is any less worthy? No.
On my Mac, using my home 50mbps connection, I cleared cache and loaded news.bbc.co.uk. iStat tells me it spiked at 350KB/s when loading. That's a whopping 2.8mbps. Does that mean my 50mbps connection is really only 2.8mbps realistically? Certainly not.
On my home connection I let a 1080p YouTube video load and iStat shows numbers all over the place, from 400KB/s to 3.6MB/s. But if I download a large file with a download manager, it stays at a rock solid 6.8MB/s, or just above 50mbps.
So to answer your question, the realistic speed you can expect will vary based on what you're doing. Watching YouTube, downloading a large file, loading a simple website, downloading an app, or loading a website filled with 50 megabytes of pictures will all yield varying speeds because of many different factors. Speed all depends on what you're doing with your connection, and how the other end and everything in between performs as well. So I can't give any realistic figures, but to find out what your connection is capable of, speedtest.net will work just fine.