Valuation is based on a whole host of things including revenue, brand recognition, distribution, customer acquisition costs, customer retention rates, switching costs, growth, etc. You could start a Dropbox competitor and have none of those. The business matters far more in valuing the company than how hard it is to replicate the product. It's much easier to make a hamburger as well as McDonald's than it is to make a business as good as theirs.

Now, try also getting millions of users, tens (hundrends?) of thousands of paying customers, tons of possitive reviews from both major outlets and happy users, Jeff Bezos investing in your company (IIRC), hundends of third party apps offering integration with your service, etc...

Oh, and the technology to do what you do, and do it AT SCALE. And also the history of having met and solved tons of technological (OS/use case/etc) obstacles in the process of building your app, now in it's Nth year.

I mean, what are you on about? Just a website and some hard drives?