the only teams that can get 'better' deals are the ones that play in Tax free, or tax reduced cities Florida/TB etc ...if Cap Hit included taxes, then you would see vast differences across the league.
a players value or worth when they sign the contract has a lot to do with it, like MacKinnon for example, he was coming off 3 mediocre seasons when he signed his deal. the day Draisaitl signed, 90% of the board screamed overpay ...do you think they will be signing 'bargain' contracts on their next deals?
Barkov is a steal right now because he signed younger and unproven, but, his next deal will be huge, though, Florida because of the taxes can offer him less and he still takes home more than if another team offered him 2 mil more per season.
here is a link to a cool calculator
Tax Calculator | Gavin Group Kuch for example pays under 3.5 mil in taxes on his 9.5 in Toronto he pays over 5 mil, so Toronto's offer would have to be 1.5 million higher for the player to get the same salary, is that system fair in a 'flat cap' league, NO, is that the reality, YES.
dont bother about endorsements or tax loopholes, because they exist in both places, the bottom $$ is all we are comparing, because that directly affects the cap hit without the 'creative accounting' for the player.