I bought two 5000mah 40C Gens Ace packs about a year and half ago when they were $24 each at Hobbypartz. It was about when they were starting to get popular. After word of mouth and a positive review from UltimateRC youtube vid, the prices just kept crept up. Sometimes they would creep down a bit, or go up a bit too. Thankfully my Gens Ace packs are still pretty strong.
Gens Ace were great value maybe a year or two ago, but not anymore. You can get very good lipos with higher mah and C ratings these days. I've moved onto Valuehobby.com lipos. Pretty happy with them for their price.
Them G-Force 2s lipos are pretty good lots of punch . Never get warm after a run on my SCTE.