Using Excelville.com, there are no costs associated with selling spreadsheets and you don't need to build and manage a separate site, which works out pretty well. Whatever path you take, I wish you the best of luck. Leave a comment and let me know how things are going for you.
Many spreadsheet applications nowadays have functionality above and beyond the traditional, offering a variety of charts, look-up tables, databases and more functionality than can be mentioned here.
You'll need to develop good marketing material. Things like demo videos, which you can find plenty examples on YouTube, screenshots, and keyword rich descriptive text help people find your spreadsheet and communicate the value that sets yours a level above the rest. Excelville.com actually allows you to upload your spreadsheet with all of this marketing material in an easily searchable and user friendly website.
Another advantage to using a spreadsheet application for your budget is that you won't have to access the Internet to access your budget. You will be able to view it or work on it wherever you are and if you typically work on a laptop computer and take it with you when you travel, this can be extremely beneficial. Using budgeting spreadsheets to manage your finances is an easy and affordable way to stay on top of your financial game.