What if his plans all along were to play out his last year
Maybe. It might not be his last year though. Tag still an option next year.
If that's his plans, so be it. It'll be impossible for him to recover the $ he lost. If he plays out all two tag years, he'll have made ~$95M over three years (from '22-'24).
Josh Allen is in the same draft class. He's going to make a minimum of $143.1M in his career through '24. If Lamar plays this out, he'll have made ~$105.2M through '24.
Pretty gigantic delta there. Even if I discount $8M because Allen was higher draft pick and thus his rookie contract was slated higher, Lamar's about $30M in lifetime earnings behind a player from the same draft class who one could argue should be "comparable" in terms of compensation.
There's no contract he can sign that's going to catch up him to that. It's highly unlikely he'll get $60M a year two years from now. And if he does, all the other guys behind him, including Allen, will get raises too.
If its a product of "he just wants out of Baltimore", then so be it. Man up, say that, and let the Ravens trade you for the best they can get.