It should be: all the way up to the 64 core threadripper scales pretty linearly for compiling. It probably won't be worth it over whatever the 3950X price drops to though, if per-core performance is really only 9% better in compiling workloads.

I mean more in price to performance. Will +200 dollars be worth the lower base clock and increased core count?

11% lower base clock, 33% more cores. The 5950X also has 100% more L3 cache.