Meh.. this meme has been copy & pasted onto Slashdot over & over again since the 90s.
1. I can tell you exactly how much Intel chips will cost if AMD is noncompetitive or goes away entirely... they'll cost exactly what they cost now because AMD is already effectively out of the game.
People forget that Intel is not only in heavy competition with ARM, but Intel is in perpetual competition with its own parts from last year and if Intel really jacks up prices they will simply lose business from people who don't upgrade.
2. You have a very selective memory when it comes to history. In the brief periods of time when AMD really had some form of a performance lead over the Pentium 4, their chip prices were as high or even higher than what Intel charges for its extreme premium parts now. FX-62 for over $1000... I'm looking at you.
AMD isn't some angel, it just doesn't have the opportunity to be the big dog very often. Additionally, even when AMD isn't the top dog they've charged whackjob insane prices for chips... $900 FX-9590 launched in 2013 as some sort of bad-joke, I'm looking at you.