The problem with making a FTB server isn't even cost, sever hosting fairly cheap. It's the time and effort required to make make and maintain one. It's heavily modded which bogs you down with extra labor from the start, but in addition to the setup there's so many extra things that can break and way more ways to cheat. it also requires someone familiar with the mods and how they can be used to dupe/grief so they can negate those items that can be used for Evil. Most FTB servers are short lived for a reason.