For the purposes of putting it into the staff, it would cost the same amount as putting an 8th-level spell into a staff.
Good luck getting that as a bard (will probably have to add +5 to the craft DC since you are unlikely able to cast that).
Staves are spell-trigger items. Spell-trigger items without meeting the spell requirements.
So, to make this staff, you need to be able to cast your maximized deafening song bolt (an 8th level spell). If you're not able to cast it, you cannot make a staff with it.
Since only bards have this spell and they cannot ever cast 8th-level spells, it seems impossible. However, if you can find a way to cast this spell, or find a way to get some 15th level spellcaster, or higher, of a different class who can somehow add this spell to their list of spells known, perhaps through a feat or class ability, and then have them maximize it as an 8th level spell and cast it during the creation of your staff, then you might get away with it.
In which case, the price is as Ravingdork said, 400 gp × the level of the highest-level spell × the level of the caster, or 400 x 8 x 15 = 48,000 if I did that in my head correctly. Plus, that guy might charge a lot of cash for sacrificing a feat/class ability to acquire a spell he might not really care about, just so he can make a staff for you.
This is getting into interesting gray area.
The Item Creation rules say "spells that must be known by the item's creator (although access through another magic item or spellcaster is allowed)". So, even if YOU don't know this spell, you can still make the item by accessing the spell from another magic item.
This is not the same thing as using a metamagic rod, but it could easily be argued as being the same thing, more or less, and therefore that same quote could apply. GM's discretion (heck, all magic items are GM's discretion, this is just doubly so).
So if your GM allows this staff in the first place, and if he allows you to use your 5th level spell maximized via a Metamagic Rod, then it looks like it should be possible.
I also thought of another (costly) way to do it: Just make a wondrous item that can cast the maximized spell once per day. There is no unbreakable requirement for you to even know the spell, so you just add +5 to the Spellcraft DC and skip that requirement, make yourself a pair of boots that cast the Maximized spell once per day, and then use that pair of boots to make your staff.
The only catch is figuring out the price of your boots. (the same question you raise in your last post). It should be 1,800 gp x Spell Level (8) x Caster Level (?) divided by 5 (once per day) so 2,880 x the Caster Level, but what is the caster level for an 8th level Bard spell? If a bard makes the item, the answer is, there is no such level so this item is impossible. But what if a wizard makes this item? He doesn't even have the spell so asking what a bard's caster level becomes irrelevant, so maybe we only need whatever caster level the wizard would be to cast an 8th level spell (15). If your GM likes this answer, then the CL should be 15 (arguably, even when a bard makes the item).
Plugging that in, I get 43,200 gp to make a pair of boots that cast this spell once/day. Now, with your GM's permission, spend 43 days making the boots then use them to make your staff.
Easy, peasy.
Spell Perfection or a metamagic rod would serve, yes. That's why I said it was unlikely you would be able to cast it, not impossible.
I had forgotten about the not being able to add +5 to the DC for spells with spell completion/trigger items and potions.
The question is, does that apply in this case (assuming no feats or rods)? Does that item creation limitation apply to knowing and casting the spell? Or does it account for the metamagic feat as well?
One interpretation of said restriction would allow it, and the other wouldn't.
One interpretation of said restriction would allow it, and the other wouldn't.
True, but making the boots first would solve that restriction either way, leaving the only concern being how to price the boots.