You'll need to include more than a basic level of development and calculation in your spreadsheet. There are lots of free spreadsheets on the web. Most of which are very simple and easy to build. People aren't going to buy a spreadsheet that they can get for free. Take yours to the next level by adding all the value you can imagine. Then research on how you can offer a little bit more on the development and functionality side.
However, companies can nowadays achieve these goals with less effort and in a cheaper way by using properly designed spreadsheets. The right spreadsheet solutions allow companies of all shapes and sizes to achieve and maintain a prominent position on the market, optimizing and accelerating a wide range of specific business processes and tasks.
Regarded as a very effective and reliable means of data management, monitoring valuable financial data, as well as optimizing processes involving frequent data entry and manipulation, spreadsheet programs have rapidly become popular among businesses of all types and sizes.
You could make money doing something you love (or like [or maybe not so much but just really good at]). It's great to see a spreadsheet come together, and usually a lot better than what you originally envisioned. Especially when the dang thing works.