If has become fairly clear that developers – from the hobbyist to the professional developer studio to the enterprise-level wonk – hate paying for tools. Sometimes that has to do with their budgets (or lack thereof). Sometimes they think they can do better themselves. 

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In many ways, it is kind of a “freemium� model targeted at developers (which is ironic considering it is usually the developers that target freemium models on consumers). Get them in with the free tools, charge them for the cloud.

What's fascinating is I've NEVER heard a developer complain about paying for GitHub.

NEVER.

Is it because GitHub is valuable or because it's priced so reasonably?

Maybe both.