300-400k I would guess. When the taming quest started I would have priced it higher but, after awhile you figure out where to find or spawn most of the tames easily. Dark Wolf and Raging Griz are the hardest to spawn and are worth the most.
I see you already have an auction started on another thread but I wanted to add my two cents. After all, the more input only helps narrow down an appropriate value. Considering people have been selling quest participation slots at 100-200k a pop, this scroll has a high potential value. So if it were full, I'd say the scroll would be worth 1-2m. Now I think 2m would be a hard sale considering the buyer wouldn't make any profit (aside from event earnings) but 1-1.5m should be relatively easy considering the buyer could sell participation slots, AND they'd get an extra bonded slot, plat, gold, and a chance for rares just by running the event. However, since your scroll isn't full you just need to do some math (ie: total value /23 * 18) then subtract a little off the top for the inconvenience of making the buyer finish the scroll. Anyways, that's just my opinion. Good luck!
To find a Griz on average takes 10-20 hours. Of course this will vary due to luck and number of people out there hunting them. Dark Wolf is slightly easier to spawn but takes nearly the same amount of time. That's why the Griz and Dark Wolf go for 200k plus. It's easier and more profitable to farm and then buy the quest tames... that is if you could find a Griz or Dark Wolf for sale.
Backstory on this.. and a free bump Scroll came from a tamer who had it in his bag [10:59:25] <Peace> or the back story is entirely made up... either way 360k is not bad at all.... Not alot of things are worth millions on this server despite some vocal opinions [10:59:53] <Unknown_Hero> It was in a bag [11:00:05] <Unknown_Hero> We guildied him then killed him then kicked him [11:00:18] <Peace> be proud [11:00:33] <Peace> you couldnt even take a count for 360k [11:01:19] <Unknown_Hero> huh [11:01:23] <Peace> No sympathy for a tamer who gets 18/23 and keeps his newbied scroll in a bag either [11:01:36] <Unknown_Hero> Lol [11:02:13] <Peace> doesnt mean they deserve to lose it, nor conned into joining a guild so you could kill him for it without taking a count ... [11:03:20] <Unknown_Hero> We also trapped his mare [11:03:24] <Unknown_Hero> So he had to summon ball it