The one thing you have to take into consideration is the E36 M3 which was a different car in the US than in Europe. BMW didnt think buyers would want to pay more than what they had for the E30 M3 and so the US E36 M3 got a torquey but reduced power I6 over the free revving I6 the rest of the world received. So pricing in Europe did go up significantly from E30 to E36 even though it didnt jump much at all in the US.
Not to mention the article is using base pricing for the E30 (35K), E36 (37K), and E46 (45K)but then uses 70K for the E92...get real. Maybe 70K fully loaded and out the door. If they wanted to use 70K then they should have set the E46K at 55k becase that is more realistic.