At every place I've ever worked that hired juniors, the juniors always have to leave by about 2 years, because the company will never (roughly) double their salary to what they can get on the open market.
That first year, the juniors are probably a net drain in productivity - for their work and the time other devs spend teaching them. Then the 2nd year, they're underpaid for as long as you can hold on to them. But the good ones will be out the door pretty quick.
The system always seemed kind of broken to me. But a shop without any junior devs is also kind of sad. If you hire the right person, it's rewarding to the other devs to teach them and watch them grow.