Is the penalty for slotless items waived on pearls of power? The price seems to indicate this is so. Therefore can I get a cheaper price by crafting them into a slotted item (for example, bracers of power)? Can I further reduce the cost by allowing them to only be used by members of my faith/alignment or only those with ranks in knowledge (religion) supposing they have to recite some relevant holy passage?
First, remember that creating non-core items is always up to the DM, never up to the player, so if you're the DM, you can do what you want but if you're not, you should be asking your DM, not us.
That said:
1. Pearls of Power have their own formula. The CRB says that not every item follows the Item Creation Rules and this is a case where that is true. Creating alternate items of "Power" should be priced based on the Pearls' price structure, as per the suggestion in CRB where it first suggests finding a similar item and using that as a pricing point.
2. Reducing cost like this is just plain cheese. Sorry, not trying to offend you. The rule very clearly is not meant to help players reduce costs - if it were, then it would be assumed that everyone makes items restricted exactly for them and always gets the discount, unless they make them for a friend in which case they make them specifically for their friend and always get the discount. I would strongly advise all GMs to never allow this discount and use it solely for GM to craft interesting items for entire races or cultures.
This was recently discussed in this thread - I think this post might be the most relevant but several others in the thread are informative too, so I won't try to re-post the whole discussion here, just click the link.
No offense taken, its why I asked. Now I am torn because the DM has verbally ok'd the rules as written. I even used the pearls of power as an example of an additional 30% off if class or alignment restricted. I may end up self.limiting to no more than 10% and put the money I save away for fluff purposes (we joke about building an orphanage from the.money we save in crafting).