Just got my GorillaPi SupaVent V2 Case for my Pi3.
Playing Minecraft 1.12 using my old case (heatsink, no fan) the CPU would reach 80-85 degrees, this SupaVent V2 case reduces the temperature to about 50 degrees
You get aluminum case cheaper, depending what you use between components and passive cooling surfaces, temperatures could get much lower than 50, even during extreme load.