Originally Posted by Gruoso 
Let us talk about real prices with the comparison of the OP (K20D vs 40D).
40D+Canon 70-200 f4 USM IS +Tokina 12-24+canon 50f1.8II+ Canon 300 f4 USM IS + Tokina 16-50 = 1100+1100+ 450+ 80+ 1200+ 650= 4580 USD
K20d+ Pentax 70-200 (ops, let us say 50-135 f2.8)+ Pentax 12-24+ Pentax FA50 f1.4+ Pentax 300 f4 + Pentax 16-50= 1300+800+650+200+1250+650= 4850 USD
That's a very unfair comparison. Not only the 50mm F1.4 vs F1.8 (the Canon F1.8 certainly can't compete with the Pentax 1.4 on any level), but an F4 long zoom vs an F2.8 one? Two third-party lenses for Canon vs zero for Pentax? And to be completely fair, you'd need all IS lenses on the Canon side - which means no 50mm and not the Tokina 16-50mm.
You can work prices any way you want and you can certainly build a K20D system for the same or less than a comparable 40D.