A number of factors can influence the actual cost of wedding flowers, including the time of year and location of the event, the size of the event, the number of different types of flowers (and the flower types themselves), the size of arrangements and how elaborate they are, how far in advance you place your order, etc. Snippet and Ink, a wedding planning blog and resource, explains very clearly what exactly can effect the cost of a bouquet, and the factors discussed apply to most other floral arrangements as well.
Usually, taking all of those things into account, the flower budget breaks out to something roughly like this for the average-priced wedding:
Bride’s bouquet: $50-200
Bridesmaids’ bouquets (each): $20-50
Corsages and boutonnieres (each): $8-30
Toss bouquet for the reception: $20-50
Church altar flowers (each arrangement): $50-75 or higher
Pew flowers (each): $10-40
Reception centerpieces (each arrangement): $40-150
Flower girl bouquet or petals: $20-35
Floral cake topper: $30-100
Extras you have like floral hair decor; decorations for outside of the church like a wreath or stair decor; extra arrangements for the cake table, gift table, etc.
For couples on a tighter budget this can seem quite daunting. Here are some options to keep your flower budget under control.
Use silk flowers or other non-floral materials. Some people think silk flowers are tacky, but I think they are a great alternative. While they may not always be a huge cost saving measure, they have many other benefits that make them a great alternative to fresh flowers.
Share your budget with your wedding planner and florist. Be up front about your budget as well as your dream wedding flowers if you chose to work with a florist. They are trained to marry the two, and as long as you are flexible about your ideas, they will be able to create something beautiful in your budget.
Multi-purpose arrangements. With a little careful planning, nearly all of your arrangements from the ceremony can do double duty at the reception. Bridal and bridesmaid bouquets can become centerpieces for the head table, the altar flowers can become decor for the cake or gift table and pew decor can line the walkway to the reception site.
Shop seasonally. Choose flowers that are in season where your wedding will be. Getting flowers that are not in season where you are will cost you premium prices.
Larger blooms. Choosing flowers with large blooms means that you will have to buy less stems to create the same effect. A single hydrangea or a couple of peony blossoms can do what it would take a dozen smaller blooms to cover.
Less expensive blooms or greenery. An alternative to using large blooms is to use lots of less expensive flowers or greenery and filler to create a large statement piece for less cost than an arrangement of the same size made totally from flowers or from more expensive flowers.
If you are flexible about your flower dream, you can have gorgeous wedding flowers without blowing your budget.