“A minimum viable product (MVP) helps entrepreneurs start the process of learning as quickly as possible.”
Many companies that you know, such as Groupon or Dropbox, did not decide to build the product when they started. Instead, they tried to validate their assumptions in the easiest possible way. In the case of Groupon, they opened a simple site on the WordPress and started to publish one offer daily. They sent coupons to people manually. They were experimenting with what was working and what was not.
Guys from Dropbox did it in an even easier way. They published a video showing all the features they were going to build. The video went viral, and this proved the hypothesis that there was a need for such a product in the market.
As you can see, it’s possible to validate many assumptions at more than 10x lower the cost of building a full product. Why not build the full product in the first place? Because it will save you time and money. You will be able to iterate fast and learn from your mistakes along the way.