Don't buy your flowers from the shop that's charging you $75 and up for red roses. While it requires a little more leg work, head to either your local thrift store or the 99 cent store and find a unique vessel for the flowers. I found these while roaming around a local thrift store:
Next, head to your local Trader Joe's right after they open at 9 am and buy a few bunches of your favorite flowers. If you have a little more time on your hands, I recommend making a trip down to the LA Flower Mart, but make sure you bring cash, because not all vendors except credit cards. Once you cut and arrange your flowers in the vase, find a piece of ribbon, yarn, or string about 18 inches long, tie it around the arrangement, and v'oila!
If this seems like too much work, I have another idea for you. Balloon bouquets are fairly inexpensive and make quite a display of affection. Head to your local party store, like Party City, and have them build a latex/mylar arrangement just for you! It shouldn't cost more than $20 - $25, depending on what you choose.
My final suggestion: Head to your local home & garden store (Home Depot, Lowe's, Osh, Armstrong Garden) and purchase a potted plant. I recommend a small rose bush, gerber daises, or an orchid. These plants will last longer than cut flowers and generally cost under $15.
And remember, no matter what you spend, it's all about the presentation.