Not much of a guess required.

A 15 year ERJ Captain makes at least $80,000.

If that Captain were hired at WN, he'd make about $45,000 that first year,
$85K the second, $95 the third, and finally break even making about $105 in the fourth year. If he worked more than the bare minimum Eagle, it would take 5 years to break even.

If he went to jetBlue, his pay cut would last until he upgraded, after at least 3 years, and he'd need to recoup about an average loss of pay of $26,600 for those three years, or about 33% of his Eagle pay.

Now assuming he has a mortgage, car payment, kids to put braces on or college tuition to pay for, exactly how does he take a 33% pay cut for three years?

It shoudn't take a financial genius to realize that the cost of making the jump to a potentially better paying job may well be prohibitive to guys who have already esablished families, and aren't living in Mom & Dad's basement.