>but instead invests that money in poaching.

give a big enough raise and they won't want to be poached. You won't retain everyone, but your goal probably isn't to compete with Google to begin with. So why worry of the scenario of boosting a good junior from 100k to 150k but losing them to a 250k job?

In some ways you will also need to read the room. I don't like the mentality of "I won't hire this person, they are only here for money", but to some extent you need to gauge how much of them is mission-focused and how much would leave the minute they get a 10k counter-offer. adjust your investments accordingly and focus on making something that makes money off that.

What's the solution? Locking juniors in with contracts? Vesting cliffs?

Compete for talent. You can never compete with big tech salaries, and often you can't compete with their benefits either. But you can still compete in creative ways. The most obvious way that no one does is to promote people into lower hours worked; instead of a pay raise you give them every Friday off, for example. There are a lot of types of people out there motivated by a lot of different things than money.

Its the tragedy of the commons. These companies will think they are very smart for doing this, but theyll just foster a culture where there are no competent employees once the current seniors retire