First it starts with the farm where the flowers are grown, they decide what and how many of each flower they want to invest their time. and money in. For instance, if they plant an entire field of hot pink teacup roses and the demand is for soft pink teacup, then they have just lost the entire crop, plow it under and start again.
Then there is supply and demand. Every florist and event decorator are having weddings and events on the same days and most have chosen the same flowers and color scheme, therefore the demand for the flower and color drives the price up.
Flowers are cut and wrapped and stored in a cooler laying of racks. No, they are not in buckets of water at least not yet. Once sold to a wholesaler they are boxed and shipped to the wholesaler who then cuts and places those flowers in water until they are sold to a florists or event designer. Shipping is pricey because the flower need to be refrigerated, flowers are not a fan of the heat.
Because your wedding is a big event, every flower needs to be at its optimum openness. Event flowers differ from daily flowers. Daily flowers are usually in a semi closed state and will give the recipient the enjoyment of watching them open over the next 3 or 4 days to a week. Event flowers need to be fully open to give the biggest show. So we spend time babying flowers to get them to open, or not open too fast or not to shed petals. We worry about our wedding flowers, but years of experience tells us that we know what we are doing and all will be perfect. We always buy extra just in case something goes wrong, or we have a handy wholesaler that we can call up.
As we prepare to assemble the bouquets and flowers we have to spend many hours doing prep work to the flowers. Each roses has to be de-thorned, leaves removed and guard petal removed. This is a time consuming task. Every flower used in bouquets has to have all of the foliage removed. Each bouquet or arrangement has to have all of the flowers that will be used in that bouquet or arrangement pulled and inspected before design can start. Once a designer starts .a bouquet its extremely hard to drop what you are dong. Once a design meets our expectations we will tie it off with ribbons. It's then placed in a cylinder vase where it awaits delivery..
All of this factors in the price of flowers, however there are other thing that factor as well, such as overhead, rent, power, water, hourly wages for designers. All of these things add up. One other factor of cost is experience, a seasoned designer will cost more to hire than someone just starting out in the business. I guess you could compare it to a mechanic. A back yard mechanic doesn't charge as much cause his overhead is lower and he doesn't have the cost of insurance and diagnostic equipment. You may have a little grease on the steering wheel and door handle but he was cheaper where as the other guy has a garage with the latest equipment, he doesn't get any grease on the door handle or steering wheel and he even put down a floor mat so his shoes wouldn't get the carpet dirty. The back yard mechanic gives no warranty and the guy with the garage gives a 30 day warranty. So cheaper is not always cheaper, some times you get what you pay for or in other words what you didn't pay for.
So think about it. You're not just paying for flowers.