exactly. it's called Inflation :)

Zeni is more easily accessible for people nowadays (due to a source which will remain anonymous in forums)
Therefore: easier to get zeni = value of zeni goes down = price of items go up to compensate

Wanna know why stones increased?

Since level 70 cap started people have been spamming tickets from gold chest....Now it's almost been a year and people ran out of keys..

People ran out of keys and now people cant get tickets....Now people have to do real upgrades.