I would think that most places that do paid deployments also have unpaid
deployments for mitigating costs.
Many businesses require paid support for contractual reasons, or as part of
support package for applications, or for regulatory reasons. I think that
some places have requirements that even if they are capable of supporting
their own servers, they always hire out for support; there own admins are
not allowed to touch the hardware.
So there are all sorts of reasons why people do support, but they paid the
premium support costs for every little thing they want to use Linux on then
that would be massively more expensive then just sticking with Unix or
going with Windows.
As far as development goes.. for busy projects you really do need full time
people to at least do coordinating and documentation, even if most of the
development happens from third parties working part time.
So I expect it's heavily symbiotic.
Maybe when the market for Linux stagnates you might see some adversarial
stuff going on, but as long as it all keeps growing then everybody should