Current Rates

Port Sarim - Betty's Magic Emporium
one rune every every six seconds
(~600 runes / hr)
max stock 300

Mage Arena - Mage Arena Rune Shop
one rune every six seconds
(~600 runes / hr)
max stock 100

Magic Guild Shop
one rune every three seconds
(~1,200 runes / hr)
max stock 50

Suggested rates/stock

Port Sarim - Betty's Magic Emporium
one rune every every two seconds
(~1,800 runes / hr)
max stock 50

Mage Arena - Mage Arena Rune Shop
one rune every two seconds
(~1,800 runes / hr)
max stock 100

Magic Guild Shop
one rune every one second
(~3,600 runes / hr)
max stock 250

Reason for boost in magic guild is because its a guild and you should be rewarded for being able to access the guild. Doesn't make sense currently why anyone can buy more runes per hour at a shop in varrock than from the magic guild lol.