A player just showed me this phase 27-3 with 9 energy for 48 recruits and 8 thousand XP, is that right?
Nope, most likely he used 3 loot tickets on this stage (so basically he would have spent 27 world energy).
Yep. S2 27-3 gives 2695 xp per run. x3 gets you 8085 xp total.