It doesn't look like Offbeat's calculation is accurate for this clip. People walking moderately usually don't sweat that much (or at all). And we know that a number of leaders have a towel in back pocket (some actually using it a lot, some just as a fashion - which we discussed in one thread)
Interestingly, I don't remember any follower having a towel in back pocket (and recently many have some kind of back pockets for storing the phone), although many of them certainly move considerably more than the leaders
It's not easy to estimate how much energy is actually being used by watching the dance - it depends a lot. Performers usually try looking elegant and effortless, so they might be spending more energy than it looks like. Social dancers on the other side sometimes want tho show that they spend a lot of energy (even if most of it actually isn't spent most efficient way due to lack of technique), which is also connected with those towels ...
So some people probably spend 10x more energy per dance than other when dancing socially and the range is like from walking slowly to running quite fast ...
Yeah, that's why when you watch someone on video, it's not immediately evident how much energy they're expending.
I'm pretty sure guys like Terry are expending a lot of energy. The sweat is one indication. There could be other non-visible factors.
I'm rarely out of breath when dancing, but the quality of my dancing does decline as the night goes on. Some of it is mental exhaustion. It's been a while since I just switched everything off since I'm always conscious of what I'm doing when I dance. I also don't really feel like pushing myself past the point of exhaustion anymore so I usually sit down for extended periods or call it a night.