I don't know about going between Mac's but yesterday I moved 30+ Gbs from an external USB3 hard drive that is plugged into my Asus RT-AC68R router's USB3 port and it took about 40 minutes. I was also watching youtube videos at the same time so I'm sure it could have been a little quicker if I weren't. But I wasn't going to just sit there and watch the status bar that whole time. My rMBP is the only device logged on to the 5 Ghz channel and connected on AC, so there should have been no other interference. I regularly see 50+ Mbps on speed tests online, but that is limited to my internet connection. I would think just a Mac to Mac connection would be even quicker.
Victor