Using a sickle is an activity I'm rapidly falling in love with. I need to get a scythe, but a good one is expensive. It's on the top of my want list. A sickle is a good starting point I think. I love the motion involved. Never been taught shit about how to use one...but I've applied aikido body movements to the equation and it seems to be working fine.
I really like my sickle too. It really has very little in common with a scythe, though. When you use a scythe, you keep your arms still and twist your hips, keeping the blade level with the ground. You end up making a wide path, generally through tall grasses or grains. Sickles are all about arm movement and working in much tighter areas.
And while a quality scythe is expensive for a hand tool, if you compare it with the cost of a lawnmower, it is really quite reasonable. The main reason I don't get one is because the town I live in requires that grass be kept below 8 inches and with the unevenness in my lawn a scythe just doesn't work well at that height. The bulk of the grass has to be above the blade for the scythe to cut cleanly, and you need to leave at least a couple inches clearance below the scythe so you don't hit rocks, tree roots, molehills, etc.