Not cost effective? They only cost $150 on sale, which is probably what the Echo will cost. I'm not following you.
If you want cheap extenders, the Linksys DMA-2100 can still be found on fleabay for $100 or less. I have one, it works. Not as well as the Xbox, but it's good enough after you disable menu transitions on it.
I wouldn't swap out a Sage setup for MCE with 4 extenders either, but cost shouldn't deter folks new to MCE from getting extenders. Ceton will probably be a much better solution when it comes out, I'll grant you.