I'll add that if anyone thinks the MarcPro (or an e-stim) is just a TENS unit, try both and tell me if you still feel the same.
I bought our MarcPro in 2014. It has been used constantly since, by multiple athletes. It's STILL in service today. The only money beyond pads I've spent is that one lead had to be replaced a couple of years ago.
As a pitching coach I fell in love with the thing and what it could do for recovery in my pitchers. I could barely afford the one I bought, so I searched for cheaper units. I actually found, and bought several e-stim units more reasonably priced ($100-$150). However, they were flimsy, poorly made models, none of which lasted more than a season or two and used up 9v batteries at an extraordinary rate compared to MarcPro's rechargeable battery. Putting aside for the moment the replacement cost, I probably lost any savings simply on batteries.