If it really would be, then current state of things would not go into "making it cheap". I think for entry level employee, or just a regular employee, cost of bad hire is not that high. If turnover on those positions is high, then it also makes things cheaper just to fill in the seat.

I have seen not that brilliant employees that still were earning company money. Just you know "we hire only best of the best" is a scam.

Hiring bad manager or a senior dev, can be bad I agree. So it is not so good to use the same hiring way for seniors and juniors, but unfortunately companies treat senior devs also like juniors.