However, in my observations and experiences, the last few years (i.e. the years when H1-Bs were allocated by lottery), due to the scarcity of H1-B visas, employers started paying a premium for employees who already had an H1-B visa and the skills necessary, because they could switch jobs immediately (as opposed to having wait 1+ year to hire someone from abroad and wait/hope for them to get through the lottery).
What made it even better was that thanks to legislation by the Obama administration, your spot in the Green Card line was now portable, i.e. even if you switch employers, as long as the new employer files a green card application, you still retained your position in the line.
As you can see, the theme has been giving more leverage to H1-B employees as opposed to the employers - and that is what the American immigration system desperately needs. In the end it's only going to protect American workers.