For a bit more detail, this sort of worked:

val dfExploded = df.explode(df("price")) { case Row(pr: WrappedArray[String]) => pr.map(pr => Price(pr(0).toString, pr(1).toString) ) }

dfExploded.show()

(I had to use "WrappedArray" instead of "Array" to get past the exceptions)

but the output had some problems (char limits in this forum are forcing be to be terse)