Again, profit margins for this sort of work are tiny. Adding significant wage costs would almost certainly consume a huge percentage of profits at which point the suppliers of capital will invest their money elsewhere.
If you are going to make such a strong claim, you probably need to back it up with data.
Google Amazon profit ($11 billion and change last year), workforce size (650,000ish) and divide. That gives you a lower bound for the worst case where all Amazon employees are warehouse workers.
Amazon earns a lot of money from quite a few things that have nothing to do with warehouse workers. In particular I have read that half their profits come from AWS. I don't think that is enough data to support your claim.
A better set of numbers to look at might be Walmarts (more of a pure retail company). They make maybe 10B in profit per year (it varies a little) with 2M workers. That's $5,000 per worker which isn't much wiggle room.
Money is fungible. Amazon can afford to pay better. The only data you need to know that is what I gave.
You’re giving a reason why they might not want to. I don’t think anyone here is arguing that they want to. If they wanted to, they would be doing it already.