Doing it gradually is not a solution, nor is beneficial in the light of account retention.
I don't think the housing costs have had any effect on account retention whatsoever. You'd have to be reeeeeeally easily upset to quit over a mostly-non-gameplay-impacting feature.

It's a whole lot slower than it was on December the 13th.
Maybe on your server, but things seem pretty normal on Hyperion. any economy issues mostly relate to the devaluing of certain rather expensive goods but they were too expensive as it was IMO.