What you demand is a price discrimination, that indeed may lead to maximization of income, but also under certain circumstances could be considered as unfair by customers, because now depending where you live - you are charged different price for the exactly same thing, and leads to cheating, grey market, reselling licenses, and lot of ugly stuff.
What do you say to everyone who paid $70 when your drop the price to $20?
I am nowhere economy expert, but I believe that in long term price discrimination may even lead to stronger salary level differences between 1st, 2nd & 3rd world countries, rather help with the convergence.
Also, I don't believe $70 is so much for what Sublime Text offers, even for IT professional in 3rd world.
Much better thing would be to simply introduce some free licenses for best plugin developers, open-source project developers, students or plugin functionality bounties. Then if you cannot afford the license, you can just spend a day or two to get the license. You can do it with the trial version.