You can take 10 when you make a skill roll "When your character is not in immediate danger or distracted".
Would this include when a character is making a magical item?
[RPG] Can you take 10 when creating an item
craftingdnd-3.5emagic-itemspathfinder-1eskills
Related Solutions
Yes, and there are several magic items that affect Concentration. It's probably best to back-figure from those as the default magic item creation rules don't always give good results for unusual items.
Check out (on the better PFSRD):
- Gloves of Elvenkind - +5 to Spellcraft and Concentration checks while casting defensively, 7500 gp
- Fortunate Charm - reroll a skill or Concentration check 1/day, 3000 gp
The gloves of elvenkind are the best compare (in fact, you probably should just use them and move along). Cloak/boots are also +5 skill items for 2500.
Now the gloves do Spellcraft and Concentration, so you have to calculate that using the "two effects on one item" cost - like Gloves of Swimming and Climbing are 6250 gp, which is 2500 (Swim) + 2500 (climb) + 1250 (50% of the second power combo cost).
Therefore the 7500 cost of these gloves is 3750 (Concentration) + 2500 (Spellcraft) + 1250 (50% of the second power combo cost). So Concentration bonuses could be said to be 50% more expensive than a skill bonus (bonus squared x 150 gp). Also, that bonus is only for casting defensively - I would assume that caveat would make a flat "bonus to Concentration checks in all circumstances" much more expensive. I have no basis for this than my opinion, but I'd go bonus squared x 500 gp - it's clearly intended to be less than a stat or save bonus, but more than a skill bonus.
In fact, there is also another more recent item that grants Concentration - Tunic of Careful Casting. It adds a +2 flat bonus to all concentration checks and costs 5000 gp. That is slightly more expensive than my guess at (bonus squared * 625 gp), but that should be pretty authoritative since it's a direct compare. (Thanks to @Hettikus for that find.)
Do its bonus stack with Aid Another's not-circumstancial bonus ?
Yes. They are bonuses of different types, and therefore stack. Untyped bonuses always stack with all sorts of typed bonuses, and also with most other sorts of untyped bonuses (the exception being that a bonus will not usually stack with itself if you would be entitled to it more than once, even if the bonus is untyped; this is known as the Same Source limitation). They could have made it an exception if they wanted by explicitly saying it does not stack with Aid Another, but that would be pointless. Thus someone using Aid Another while having the feat effectively doubles the bonus that they offer.
What does mean "your assistance doubles the gp value of items that can be crafted each day” ? Do you craft twice faster (thanks to a very twister way of reading "double the gp value you can craft each day") ?
That’s precisely what it means. Actually, you craft a little more than twice faster because you are hitting a higher DC thanks to the feat’s +2 circumstance bonus, but that particular line doubles your speed compared to if that line was not there. Your progress on any crafted item is measured in silver; when the silver value of your work crafting the item is equal to the value of the item in silver, you are done. If your crafting checks produce twice as much silvers’ worth of progress, then you will meet the item’s value in half the time.
Why is Cooperative Crafting a feat?
A good question; to my mind it’s not very good design. Aid Another was already sufficient, I think, to model someone helping you out. If anything, I would have made this sort of bonus contingent on hitting higher DCs with your Aid Another roll (since, as you say, DC 10 is remarkably easy to hit), and for having both people have the relevant feat. This seems like an unnecessary feat tax to me, even if the effect is reasonably good.
On the other hand, I’m not too familiar with Pathfinder’s options in this regard, but if there are enough effects out there that stack and reduce crafting times or crafting costs, that can lead to very overpowered characters if they can get them all (see 3.5’s Artificer). Which makes me leery of an effect that doubles crafting speed, particularly when you don’t need to take the feat yourself; a cohort could take it, you could hire an NPC who has it, or whatever. Alone, this feat is fairly week. In combination with other, similar feats, it might be overpowered. Which again would just lead me to wanting to have a lesser effect, achieved just by hitting higher DCs than 10 on Aid Another.
Best Answer
Yes.
There is a nice discussion of this very topic here.
You can take 10 any time you are not rushed or distracted. It counts as your one roll and takes no extra time. Use this when an average roll should suffice to let you succeed, but a low roll would fail.
On the other hand, Take 20 is something to choose only if you have enough time (takes 20x as long), and when there is no significant penalty for failure (you take all penalties before you are successful).
Taking 10 and Taking 20 - from d20pfsrd
The real question is whether you have enough ranks and skill points to beat the DC for your magic item with a 10 - easy to do with lower CL items, of course.