If you use a hosting provider like Godaddy or Liquid:
Call them and find out what it takes to get a cert installed and spend that mo-nay right now. Its probably worth the ongoing cost.
If you're using S3 for website hosting:
Hang on to your hat, because it will cost you a fortune: http://aws.amazon.com/cloudfront/pricing/
If you're using managed hosting like Azure or Heroku
None of these options is very cheap, but Amazon, wow. Anyway, its probably totally worth the investment, so get on with it and add SSL to your site.