It only takes 20% of your marketing efforts to attract 80% of your leads.
And it requires the other 80% of your marketing efforts to retain the top 20%—i.e. keep them engaged and interested.
The same rule also applies to recruiting for a job. Then again, recruiting is just direct marketing at its finest.
It all comes down to how much quality you want to bring in. If you want average leads, disengaged customers, uninterested employees, then by all means (or not) go the cheap route.
But if you want remarkable customers, the kind that will wait in long lines for you, then you're going to have to invest more.
Same goes for hiring. If the success of your company depends on the quality of your talent, why would you hire just anyone? Why not invest in not only finding talent but retaining that talent?