RE: what is a cheap f3a 5S 5000mah battery
I have no doubt that these are fine batteries, however even with a discount the 5000mAh 25C's are still $144.50 each, or $289.00 for a pair for a 2-meter model.
I realize there are a lot more factors to consider (recharge cycles, guarantee, customer service, etc) when looking at the cost, but coming out of the gate they have a hard time competing with "fairly decent" batteries at $80 per set for us cheapskates.
Among my battery sets are several of the cheapies that have well over 100 cycles and are still going strong, as in strong enough to fly the Advanced sequence that I fly, and maybe Masters, although almost certainly not enough for F3A P or F.