Leslie is right.
Flowers arent expensive because of a monopoly or conspiracy or anything. Its their to-sell lifetime.
Flowers are perhaps the only commodity that HAS to be sold within 2 to 3 days after its picked from the 'plantation'.
And most of the flowers you buy come from overseas. Be them from Colombia, Holland, Ecuador, etc... they have to not only cross the ocean but also pass inspections, be transported via air and ground...and all of this in special containers that keep them looking fresh as long as possible (which is only 2 days or so).
That fast shipment is expensive. The special containers are expensive. And then they have to be sold quickly and making a profit. Not all flowers will be sold before they wilt so out of the 1000 flowers a store may sell, maybe only 400 will be bought 'in time'. So the price goes up accordingly.
Go and buy flowers and see how long they last in your house. Heck, put them in a glass of water and put it in the fridge and see how long they last before they wilt. Not more than 3 days after you buy it, and the flower will be wilting and losing color the whole time.
21 red roses for $71 is expensive though. Dont buy flowers from florists or love muffines that will charge for you 'flower arrangement'. Just buy them at wal-mart