Ask HS: Is Microsoft the Right Technology for a Scalable Web-based System?

This question was asked over email and I thought a larger audience might want to take a whack at it.

I have a problem I’d like to have your view on. I’ve looked around a lot, and I haven’t found a definite answer. The question is this:

Is it true that for a scalable web-based system targeting millions of users (hopefully), using Microsoft technology(.Net/SQL Server) over open source technologies like python/ruby/php and mysql (mariadb) / postgresql will cost you more? Is there any justification for paying up for Microsoft licenses(OS, SQL Server, …)?

I am in charge of selecting the technology toolbox for a startup which is going to build a scalable public web platform. I’ve worked as a developer and database developer/admin (mainly as a DBA) using different platforms and technologies, but my main focus is on Microsoft technology. I’ve considered all other important factors for this decision, and at the end, I always come back to the question of money. When I finish developing the first stage of the system, and present it to possible investors to raise money and expand it, will it be a negative point(or even a deal breaker) to have a system developed on top of Microsoft technology stack?

Every time I decide to go with Microsoft, I ask myself “why no other major web-based system (other than stackoverflow) is built on Microsoft technology?”, and I’m back to square one.

Thanks for your time.

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