Rank 4 - Enginseer lists one Sound Constitution for 200.

Rank 5 - Tech-Priest lists one Sound Constitution for 100.

I assume this is a typo. I see nothing in the errata about it.

My only question is, should it be 200 for the rank 5 or 100 for the rank 4?

The errara (found here ) doesn't say anything. So I'd say that it is simply available at different costs at different ranks. If you reach rank 5 without taking the rank 4 sound constitution, all it means is that you can purchase one for 200, the other for 100.

Well that's silly. After all, every other class has price ascend, not vary. But it's not like it's terribly important.