Wait until you do Flawless Stars and Perfect Stars
I've cubed all the way from Square Emeralds to Perfect Stars. It's at least 20 minutes of clicking (watch TV while you it) but a good return on time when it saves 500k - 1M (and this is for using not selling). I look for when Square Emeralds are cheap and buy 486 of them.
Don't cube up to Radiant Star, it's cheaper to buy from AH.
The fixed craft cost for Perfect Star is just over 5M. Those blacksmiths must be rich by now!
Its cheaper but takes time, you can also make a decent profit out of it.
see how much a perfect star sells for (-15%) then see how much all the gems, tomes and blacksmith fees would cost you, if its less then the price of a perfect star -15% you can make a profit by some simple mindless clicking.
About a month ago, star emerald GAH prices spiked up to about 900k on NA. I sold 8. After all costs and the 15% gold sink, I made well over 1 million gold. I haven't figured out if I would have done just as well selling them here with no spike, but it goes to show that you can make a profit on the GAH as well.