Spending hundreds of dollars on invitations wasnt something I wanted to do. We had a fairly casual wedding, so having fancy invites didnt really matter. I just went to the local newsagent and bought a notepad of really pretty invites. I think I paid $10 for 100 invites and envelopes.
If you'd rather something a bit more fancy, there are a few things you can do...
DIY isnt always cheaper. A friend ended up paying over $300 for 70 invitations by doing it herself. It took her over 12hours to make them all up!
If you do want to give DIY a go, try DIY invitations. They have some really easy, step by step instructions on how to make simple but pretty invites
Vista Print are great. They often have deals where you can get the invites for free, you just pay for postage. I made my thank you cards (100 of them) for under $20 including postage
Try ebay. I've sent many invites there for around $1 each. Some give discounts for bulk orders
I will invitations is run by a friend of mine, Gayle. The invites are beautiful!
There are a few different programs online that let you make your own invitations. All you need to do is get some pretty paper and print them out yourself.
Smilebox lets you make invites online. You can then email it, add it to forums or even your blog.
Free Printable wedding invitations lets you download templates of a few different types of invites and personalise them