I would never buy relic/mythic/ergon currencies , unless I was super rich and wanted to treat myself.
I don't see buying currency as "treating myself." I see it as making a long, eventually tiresome task shorter. Treating myself is buying an ice cream. I would not liken buying more RME currency to buying an ice cream. I am not and never was "super rich" but bought currency whenever I could because it sped up the process and for no other reason.