Where the money goes
Count first. The number of pieces, bouquets, boutonnieres, corsages, centerpieces and ceremony pieces, drives most of the cost. A wedding party of twelve with fifteen reception tables is a different job than a small family wedding.
Then the flowers. Garden roses, peonies and orchids cost more than spray roses, carnations or greenery-heavy designs. Out-of-season flowers can cost more or be unavailable. Season also affects demand, since spring and fall Saturdays are busy.
Finally, labor and setup. Some florists deliver and set up at the venue, then come back to clear. Others prefer pickup. Ask what is included and whether anything can move from the ceremony to the reception.