In this day and age, budget is the word, and unfortunately there's no easier way to blow your budget than using fresh floral centerpieces. On the bright side it forces us to become a little more creative when it comes to setting the table. Pictures from The Knot.com and a British wedding mag.
Centerpiece Money Saving Tips:
- Up the romance and save money by filling the table with inexpensive tealight candles. I usually get large packs of tealights from Ikea for around $2/bag. I think groupings of 3 look best, especially on round tables.
- Consider purchasing the containers (ie vases, urn, etc) instead of renting from your florist. You can get really nice glass vases from some places like Ikea. Providing your own vases can definitely save tons of money (depending on the ones you pick of course). We saved about $30 off the price of each of our centerpieces by getting copper urns on sale from Michaels.
- Use flowers that are in season
- Consider inexpensive fillers that are still elegant like hypercium berries and galex leaves.
- Stay away from labour intensive floral arrangements. For example small pomanders (round balls covered with flowers can cost $75 or more. If you love the pomander look, try using a less expensive flower like carnations, or mums.
- Pile up your favours in the middle of your table on a cake plate instead of purchasing a centerpiece
- If you're looking for visual impact, renting table linens can sometimes do a lot more for the room than the actual centerpiece. You can find nice linens starting from $15 per table.
Here are some centerpiece ideas under $20:
You can get a lovely pot of orchids from Costco for $14.99. Personally i'd recommend to wrap the base in a strip of shantung silk, or pretty paper to get an even bigger impact. 
Using inexpensive potted herbs, or grass with one or two blossoms of gerbera daisies is a charming and fresh centerpiece.
Try to find centerpiece vases or troughs that can be a part of the statement, so you dont have to spend as much on flowers.
Another example of that is this cute tea tin as the vase. There's no better way to add charm and personality to the table than taking the usual and making it unusual.
Isn't this teacup and saucer an adorable centerpiece for a shower!?
Taking small bunches of flowers and putting them in fabric wrapped cans (even washed tin cans) can make it seem as though you have more flowers on the table.
I love fruit centerpieces because there's so much colourful impact, yet you can buy them cheaply by case from your local grocery store or chinatown. Bonus- these can be done ahead of time, or easily by helpers on site.
I love this arrangement! What a deliciously fresh mix of peaches, apricots, cherries and leaves. 
Loving this acorn napkin ring idea- just in time for American Thanksgiving.
