At least in microeconomics 101, companies hire as long as the marginal revenue equals the marginal cost of the employee. If the marginal revenue per engineer is high, companies will try to keep hiring them. The demand for engineers goes up, and so does compensation.
In microeconomics, the firm would use marginal gross profit not marginal revenue [sales].
Think of Amazon, Walmart, or any firm with significant COGS [cost of goods sold]. It's clear that they can't hire employees inline with marginal revenue.
