I'm bringing in a 7th level wizard in an upcoming campaign, and I wanted clarification on the arcane builder discovery from UM. It says that
"You create items of this type 25% faster than normal..."
I need to know if this stacks with crafting at half speed. For example, creating a +4 Headband of Vast intelligence would take 16 days of work normally (or 128 hours of work). If I add 5 to the DC, however, I can instead craft at 4 hours per 1000gp in the base price (64 hours\50% of normal time). Now, if I use arcane builder, does that get me 25% off the accelerated crafting time (48 hours\37,5% of normal time) or do I add that to the 50% I get for increasing the DC by 5 (32 hours\25% of normal time).
Looking at the RAW, it seems like the 48 hour version is right, as Ch15 says:
"This process can be accelerated to 4 hours of work
per 1,000 gp in the item’s base price (or fraction thereof ) by
increasing the DC to create the item by +5."
... and then you'd take 25% off of that crafting time, leaving you with 37,5% of the original time (50-50/4=50-12,5=37,5)
The easiest way I would do this, is take the value of the item (since that is what determines when you finish) multiply by .75 and use that as your new target for finishing the item. Make your craft checks however you would until you hit that number.
So crafting a +4 headband of int normally takes 8,000gp value of crafting to make. If you were a arcane builder of wonderous items, you would use 6,000gp as your target production before finishing.
At our table we keep the number of days as static. The limitation of 1000gp per day of progress is static no matter if you accomplish that amount of work in 8 hours, 4 hours or 3 hours with arcane builder+5dc.
The idea behind the 1000gp per day limit seems to be that making more progress than that in a day is tiring work. Fast crafting means being very focused and efficient on the task, which is more challenging (same amount of work not done calmly or lazily...) but adding +5 to the dc in no way means you could spend the full 8 hours crafting twice as fast and turn out 2000gp of progress per day.
While arcane builder is simply such a familiarity with the nuances of crafting magic items that even further time efficiency can be had, while the amount of fatigue of having made that same progress per day is static.
And of course hedge apprentice doesnt speed things up at all, simply means the familiarity with the nuances of crafting allow the character to get the same amount of progress done while creating less 'waste' of the necessary materials.... This doesnt reduce the total number of days required to craft something at all, simply the amount the character would have to have invested in order to start the crafting process in the first place.
Keeps the number of days to craft a magic item static, which keeps people from trying to break the 1000gp progress per day cap, while allowing your daily crafting time to stay below 3 hours, reducting the chances of being interrupted.
What this amounts to is
Works well for us... YMMV
TLDR: At our table if you were trying to make an 8000gp item that would take 8 8 hour days to craft, neither the +5dc or the arcane builder feat reduce the number of days required, but instead simply reduce the amount of daily time investment. from 8 to 4 or 3 hours per day not from 8 to 4 or 3 total-8-hours-of-crafting-days required, under the pretense that +5dc and arcane builder dont cut the amount of work needed to be done in half or by 25% but only cut the amount of time required to do that work. but the amount of fatique that comes from making 1000gp of progress per day is static whether its taking you 8 hours of crafting on cruise control, 4 hours on redbull, or 3 hours on redbull and experience and natural arcane aptitude.
At hour table an item that takes 8 days to craft cannot be done in 3 days, but can be done over the course of 8 days working twice as fast for half as long with the +5dc or in 3 hours of crafting per day with +5dc dedication and +25% arcane builders familiarity/insight with the crafting process, arcane aptitude, and organizational skils, but the 1000gp per day of progress stands regardless.
It's certainly not 'RAW' but our gm much prefers than I can create a 16000gp magic item in 16 days using 3 hours per day at night on the road with my sustenance ring than he would me making a 16000gp item in 6 days while unilaterally blowing 8 hours of each day crafting. The tradeoff I make for being able to squeeze out a full 1000gp of crafting in 3 hours on the road is that i'll never make a 16000gp item in 6 days (and this comprimise helped our gm not to really bother with the half progress while crafting on the road since i'm both in a secure shelter and , and i'm crafting in straight uninterrupted shots because the gm doesnt feel that strong urge to interrup my nightly crafting since i'm not trying to rush it) I'm ok with that comprimise... Again YMMV.