That misses the point, doesn't it. The point isn't "maybe you don't really need nosql/non-relational", it's "maybe you don't need an expensive managed storage solution built for massive scale."
Spanner was indeed built for massive scale, which is reflected in the price.
Spanner does have somewhat less scale than their NoSQL offerings; and even Google says internally to go for the somewhat less scale-y spanner than them. (Because it's easier to react to needs for scale laten than it is to live without transactions and relation querying.)
Spanner was indeed built for massive scale, which is reflected in the price.