The price is not tied to the diff.,Diff is going up cause bitcoin miners are pointing their gpus to lc and blocks are found more quickly.Thats what drives it.
then what is price tie to ?
certainly diff is one factor, the more diff, coin harder to get, and price should go up unless there is manipulation
that is why diff goes up make block harder to be found when hashrate remain the same
when something is harder to get its price usually goes up unless someone is manipulating the price through cartel or some other shit