So, yes, most microsoft products are incredibly damaging for a startup.
Not every startup has to work with the small amount YC hands out. I know of a fair amount of startups using an MS stack, and they are doing very well. Of course, they are not SV cool, but they are making good money. You should sit back and analyze what you just said, because it is a pretty strange point to make.
My current company uses extensively .NET and I have almost a decade of experience working with it at my last employer, where I was also responsible for choosing and buying such products.
In my last employer (government), we didn't choose .NET, microsoft won the contracts. In the last update when I still worked there, we spent 250k USD to update our programmers VS to 2010 + windows 7. (I wonder if they will now update again). SQL Server prices are similar to oracle's with similar features.
In my startup (not a startup anymore) I had to spend 40k just to get the environment needed for a project (involving telephony) the only reason we had to use .NET was because the hardware manufacturer only provided driver+tooling for windows and some components were exclusively for .NET. Because we mostly use linux and macs, we also had to buy windows licenses. In my country, a Windows 8 license cost almost 2x the minimum wage.
We happened to have a discussion if we should give up or not a specific product because of the microsoft taxation on our business. The only reason we decided to keep using .NET is the cheap labor and the lack of hardware suppliers willing to provide us drivers and tools for linux.
So yes, microsoft damages not only startups, but companies in general.
I don't know much about IBM products but I'm a heavy Oracle DB user in the process of migrating to Postgres due to simple problems, cost not being one of them. In fact, you will see a lot of users still using very old Oracle versions and getting full support from oracle.
Not every startup has to work with the small amount YC hands out. I know of a fair amount of startups using an MS stack, and they are doing very well. Of course, they are not SV cool, but they are making good money. You should sit back and analyze what you just said, because it is a pretty strange point to make.