Ask HN: Low cost option for making product demo?

Effective means to get people to add detail to their questions?

what product? toothbrush or condom?

Look into IDEO (a world-class design firm) and their prototyping methods. They're really good at getting to the core of an idea with the limited materials available (as an example: they prototyped a surgeon's tool with a sharpie and some tape.)

We building a web app, now we want to make story telling demo video. So what are the low cost options we have ?

DIY with a screen recording product like Telestream/ScreenFlow(Mac) or TechSmith/Camtasia(PC). Record a walk through of your web app (or mocked up screens), while also recording yourself doing the voice over.