I don't do a whole lot of data analytics anymore, but I'd say: Start with figuring out how much data you actually have. We still see companies claim to have vast amounts of data, but in reality they are talking about less than a TB of data, frequently just a few 100GB. When you operate at that scale, just chuck your data into whatever database you're comfortable with and do SQL queries, it's fine.
Once you hit the scale where you have "enough" data I'd agree with many of the other comments: Managing open source or home grown solutions quickly become more expensive than just paying for a service. Not quite the same, but we considered deploying a few solutions on OpenStack, but once you paid for training and staff it turned out to be cheaper to just give VMWare more money.