depends on inventory and training
There is no magic planks in runescape. Only plank, oak plank, teak plank and mahogany plank.
Look up a magic calculator, then how many times you have to plank-make from 86-99 magic, then add the prices of the planks + runes to cast the spell together, to get the cost.
The magic tree seed costs around 300,000 coins. Search the item on the Grand Exchange to get the current price.
The price changes everyday for pretty much every item in runescape. So by the time I would tell you the price would probably be different.
250xp per log
Roughly 1.3million
The market price for one Magic log is approximately 1,360gp - 1,504gp.
In Runescape, You receive 65 Magic XP for every High Alchemy spell that is cast.
99k
Magic Logs give 303 xp per log when you burn them.
It cost about 35 or 45 magic coins
Prices change constantly, i would say 20k-30k.