3 weeks is indeed really quick to jump to conclusions in my opinion, and a lot of people just give up too quickly. In my case, it took around 10 /months/ to experiment and understand how to properly sell my Saas [1], and now we are starting to see a nice increase in sales.
Rob Walling cut a normal SaaS growth in 3 phases: build, learn and scale. The learning phase is about learning how to properly convey the value, tune your message, and find the right channels to sell your product - and it can take quite a bit of time.
Too bad a lot of technical people just stop too early (not assuming carrying on in that specific project would have been a good idea :-)