I didn't see anyone else comment on the flowers, but in all of the conventions I have ever been to, you had to pay a "suggested donation" for ANY of the flowers/plants. The last DC in CA that I attended, the brothers formed a long line from the field up to the seating area out to the open air plaza where other brothers and sisters had contribution boxes conveniently set up. They passed the flowers and plants from the field up to the selling area. I noticed the bros and sisters reading from a sheet of paper that described the type of flower and what the "suggested" donation would be. No donation, no flowers for you!
I wondered if the price they asked for the flowers was for the actual cost of them or if they padded it a little to make a buck or two. They probably padded it I'm guessing.