When did it become acceptable to write nonsense like that? How can something be five times less expensive? What is wrong with saying "one fifth the price?"
It's not just this author, I see this in print media everywhere.
To me, 5 times cheaper implies the starting point is not price of the thing being compared to. "5 times cheaper" sounds like it could be 80% of the price of normal methods.
Method A: $1005 Method B: $1000 Method C: $975
Method C seems to be 5 times cheaper than Method B.
Is there some phrase in stats used to describe this nonsense?
Yes, the language "five times cheaper" is imprecise, but common sense says they probably mean the simple interpretation.
In fact, because they aren't speaking precisely, it isn't reasonable to apply some kind of super technical methodology to interpret what they're saying.
Method C provides 5x greater savings on the cost when compared to Method B. It does not mean that the actual cost is 5x less.