it is my unsolicited opinion that "spend now, save later"
if you can make that Enigma, make it. It will make your d2r experience more fun, across more builds.
because, you can always run LK for runes ... it's just a matter of time and effort. Luck, yes, but in the end you control the amount of drops to some degree by the amount of time you put into it. Having Enigma makes that process even more doable and fun.
also, in my experience, while you're making more builds and playing the game you will experience high rune drops from time to time anyways and you will slowly rebuild your high rune stash.