from https://www.reddit.com/r/runescape/comments/4dovqz/runecrafting_xp_from_buying_450_th_keys/
"So 450 keys (300m gp) for 700 boxes with 252 left over, I got 5600 ish xp in rc w/o boosts..
56 gp/xp LOOOOOOOOOOL"
Original message details are unavailable.
Used the rift boxes on runecrafting, took 30 minutes with Wisdom Aura and bonus XP.
[..]
In conclusion, spent around 300m on practically instant 4.6M RC XP
Original message details are unavailable.
took 30 minutes
Original message details are unavailable.
practically instant XP