Wouldn't it be uncharitable to assume that the commenter is totally selfish and short-sighted? :p

It may be a cliche, but it's all connected. In a general sense, programmers at different experience levels are at least partially substitutable goods. A crash in wages on one group will probably affect that other.

In a more specific sense, companies won't pay seniors for skills at mentoring and managing the juniors they won't have.