The private repo pricing was what drove me to try an alternative to Travis in the first place. The cheapest private repos plan is $70/mo now and, if memory serves, when I looked into it previously it was >$100/mo.
Fine for startups I guess. For the use case of someone who wants a CI server that, say, runs tests on their Project Euler private repo it's a no-way-no-how price point.
I assume they've thought this through and it's done purposefully. Still, side projects tools are a gateway to real project usage.