For that reason, it's pretty much zero. It sounds good but it doesn't math out in terms of the monetary magnitudes involved. (And this is why you should not get your economic news from bubbles.)
If labor1 is replaced with labor2 at a higher salary with no increase in productivity (no direct reason why productivity would go up simply from hiring other people), earnings go down, because earnings = revenue - expenses, and salaries are part of expenses.
Another way of seeing it is that "typically" for a given business, the rule of thumb is that 1/3 of revenue goes to owners, 1/3 to workers, and 1/3 back to keeping it going. (This is correct within an order of magnitude.) The money that goes to owners is called "earnings" and you're directly asking to change the earnings/salary ratio here.
Since Earnings are the denominator in P/E, then decreasing earnings increases P/E insofar the market is willing to tolerate that. If not, then P follows E downwards.
This basically leaves second-order effects. Ford famously paid a higher wage to his employees so that they could afford to buy the cars they were making. This works well in those old-fashioned company towns which were effectively closed systems. Money had to circulate. If labor2 now earns more also spends more to boost revenue, then even if the earnings/salary ratio changes, earnings will get lifted on an absolute scale. The pie may be sliced differently but overall, it's bigger. Again, this is unlikely because goods and services can simply be exported elsewhere. It is no longer a closed system.
Overall, the main problem with this whole line of thinking is the lack of math and proportion. We're talking about replacing something like 1% of the labor force and the unskilled and low paid (<$8-15/hr) at that possibly getting a slightly higher salary. As a slice of the overall economy it's immaterial even though of course for an unemployed HS dropout that now lands a $20/hr job at a meatpacking factory or gets a job as a roofer or an apple picker, it would make a big personal difference.
If you want to understand BIG impacts on the financial markets, you can safely ignore the poor (not trading stocks) and the rich (also not trading because buying and holding for generations). Focus on what the middle class is doing (via their pension funds!) and where their money goes in terms of spending and saving.