Charging the change fee to upgrade a ticket is actually something relatively recent (they slipped this in last year).
When a customer wants to pay the difference between a lower fare and a higher fare (to qualify for WBC upgrades or date flexibility), it makes NO BUSINESS SENSE whatsoever to nickel & dime a change fee (or in this case, $100 to $300). NWA is losing out on real revenue with this policy because customers who want to upgrade to higher fare basis tickets are going to be super ticked off to have to pay the additional change fee.
This shouldn't even be thought of as a possible "perk" for elites, they should get rid of the change fee for upgrading tickets for everyone, period.
I wrote a letter to Customer Relations about this a couple months ago.