Hidden- why? Because it is labor that occurs but that is not witnessed by the client. Processing and prepping flowers for a wedding or any event, requires a LOT of time and labor. For instance, I received flowers for a wedding. I processed them (meaning unpack, cut stems, dip in hydration dip, place in preservative water, move buckets to front of shop.) For one wedding this took two and 1/2 hours. Mainly because I had to process 100 stems of gerberas. For more on how those little fickle flowers are processed, see our blog post: Gerbera Blog Post
At the end of the first day, most of the flowers are placed in the cooler and organized by what will be used first. Some flowers stay out to open up; like lilies and alstroemeria. In order to get them to open quickly they require being recut and changing the water at least twice a day if not more depending on what open stage they are at.
Closed:
Open: 
The next day I pull out the buckets of flowers I need to further process /prep. Roses need dethorned. Lilies need pollen sacs and lower foliage removed. Lilies and alstroemeria recut and seperate the open from the closed, open goes into preservative, closed stays out all day until it's "ready to party" as my supplier and I have termed it.
Everything I outlined above is normal for every shop for every wedding. But I can't charge a "processing" fee based on how many times I will be handling the same flowers can I? So therefore we have a specific retail markup on our flowers(which covers our cost + shipping) plus design & labor costs that combine to give you the final wedding bouquet price.