The title explains all (:
I’ve never used it inside Unreal, but it is free if you use it outside and then import your assets. So maybe that means a little more work depending on your workflow and your use of it, but I can’t speak to the value of the SDK version.
It is good software but, if I was an indie and on a budget, I’d just try to model stuff a bit better
I’ll assume that they don’t list the price up-front on the website because it’s expensive… always puts me off.