It does depend on the occasion, but lecture notes are rarely just handed out, but cost a small fee.
Usually, lectures last anywhere between half an hour to a couple of hours.
All of the lectures I have attended have been with magic societies that I have been a member of, so the fee for the lectures was very small or sometimes even free, but the society membership fee also partially goes towards lecturers over each year.
Workshops can be much bigger than just 10 people. The real difference is the hands-on feel of a workshop. In a lecture, you are merely watching and listening most of the time, whereas a workshop involves a lot more participation as you try things out for yourself.
Joe