Using OSRS price guide as a general guideline and my experience with XP rates.
lets say 400k xp/hr with red chins, void, range pray
30 hours on medium fuse (rapid) is 1200 chins/hour
Runescape 2007 Gold
1200 red chins, 23 pray pots and 2 range pots per load. at 400gp/red chin and 9k/pot you’re looking at 21.15M or 1.76 gp/xp
Don’t forget you can bring a cannon in Zooknock’s tunnel.
let’s go ahead and say grey chinchompas are 325k xp/hr with void and range pray on medium fuse.
40 hours or 48,000 chinchompas
18.6m or 1.55 gp/xp
time difference of 10 hours, cost difference of 2.55m
If you can make 255k/hour I wouldn’t worry about using grey chins. if you were to start from 73 range and a bank valued at 0gp with the minimum earning power of 255k per hour, it would take you 113 hours to achieve 99 range. at 500k gp/hr it becomes 82 hours.
numbers lol. the next best method is generally around 50k xp/hr without pots, giving you 260 hours for a baseline, making 85k gp/hr a minimum to use grey chins and cost savings of 45M with red chins if you earn 255k/hr.