For 30 gallons, it would probably be very close to the same price. The eco would be easier though, for sure. I was just trying to add to you list of options. If you ever do a bigger tank, this would be a much more attractive option.
For my 125, I spend $5 for two 5 gal buckets of sandy loam at a landscaping place, $13 for a 50lbs bag of turface at another landscaping place, and $10 for some pond fertilizer tabs. I didn't bother with mineralizing the soil. My guess is you will spend around the same amount for you 30 gal tank on the eco.