I picked winegrapes for $6.50/hr a few summers ago (I am an American, and I volunteered to do it!). Did it mainly for the experience. It was hard, hot, backbreaking work. Not difficult, per se, but hard on the ole' spine. Doing it for a couple hours may be "fun," but doing it for 6 or 7 is generally considered "work." Then you have the occasional shear that rears up and bites you on the finger. Not pleasant.
I pick and can berries for two weeks every summer. I have picked for several hours a day for the last few days (pre-season).
At peak season, I will pick all day, then make and can jam until I drop each day.
I will pick and can 21 acres of berries and grapes--90% BY MYSELF, 10% family labor--over two weeks.
Picking is hard work, but it can be done BY ANYONE who can move his arms, including 10-yr-olds.