You can spend about as much as you want on flowers and seeds to plant. If you use pots, it's usually $10-$30 per pot, so you can imagine how much that might cost for an entire flower garden.
Not only do you want something stylish that matches your interior style, but you also want a pot that will happily accommodate your plant and allow you to take care of it without too much fuss.
Choose the deepest pots you can. Plant pots and windowboxes are easy and cheap, but why not use your imagination and recycle - how about using decorative tins for salad leaves, or wooden boxes for ...