Currently, the elite diary reduces the cost of turning a battlestaff into a mystic staff from 40,000 to 20,000 (30,000 with hard). This is essentially a useless reward, as you'll likely never need to convert a mystic staff more than a few times, especially at that end game level.

Assuming you craft a battlestaff from Zaff for 7000 gp, and you convert that battlestaff into a mystic staff for 20,000 gp, that mystic staff alchs for 25,500 gp, which then results in a net loss of 1500gp. This is in contrast to just alching the battlestaff, which alchs for 9300 gp from a 7000 gp cost, resulting in a 2300 gp profit.

Currently, this price reduction results in a net negative gp loss. I propose this price reduction be lowered to 16,000. (as well as letting noted staffs be converted)

7000 initial battlestaff 16,000 mystic staff cost = 23,000 net cost

The mystic staff alchs for 25,500, resulting in a 2500 gp profit, as opposed to the 2300 gp profit of a normal battlestaff. This results in a 200 gp net profit from this proposed price reduction.

Assuming you have the Varrock Elite diary, this only results in an extra 24k per day from the 120 battlestaffs. I believe this wouldn't be very OP as making daily battlestaffs is already kind of annoying as opposed to just doing seaweed runs and blowing glass for crafting xp.

Again, this change would just bring a 200gp profit increase to each alch, the price of nats is completely irrelevant to this suggestion. I'm just trying to make the elite diary reward a bit more useful.