This calculates the profit/loss of paying Thormac to change a battlestaff into a mystic staff. It normally costs &0000000000040000000000 40,000 per conversion, but this is reduced to &0000000000027000000000 27,000 when wearing a Seer's headband 3.

Battlestaff	Battlestaff cost	Mystic staff cost	Profit/loss (no headband)	Profit/loss (headband)
Air	8,620	38,967	&-1-1-1-1-1-1-1-1-1-1-1-10-7-6-3000000 -9,653	&0000000000003347000000 3,347
Water	8,757	25,020	&-1-1-1-1-1-1-1-1-1-1-1-3-4-8-4-7000000 -23,737	&-1-1-1-1-1-1-1-1-1-1-1-2-1-8-4-7000000 -10,737
Earth	9,021	25,064	&-1-1-1-1-1-1-1-1-1-1-1-3-40-6-7000000 -23,957	&-1-1-1-1-1-1-1-1-1-1-1-2-10-6-7000000 -10,957
Fire	8,993	24,590	&-1-1-1-1-1-1-1-1-1-1-1-3-5-5-1-3000000 -24,403	&-1-1-1-1-1-1-1-1-1-1-1-2-2-5-1-3000000 -11,403
Lava	9,835	47,747	&-1-1-1-1-1-1-1-1-1-1-1-1-3-1-9-8000000 -2,088	&0000000000010912000000 10,912
Mud	359,882	330,059	&-1-1-1-1-1-1-1-1-1-1-1-70-9-3-3000000 -69,823	&-1-1-1-1-1-1-1-1-1-1-1-6-7-9-3-3000000 -56,823
Steam	137,866	180,208	&0000000000002342000000 2,342	&0000000000015342000000 15,342

*Note: You can buy up to 100 battlestaffs of a given type every 4 hours in the Grand Exchange.

Warning: do NOT expect any of these to be profitable. They normally sell for well below the GE asking price.