Items that give bonuses to stat other than enhancement are not supported in the item creation rules (like skill bonuses, but that is a different argument)
Righteous Might gives bonuses above and beyond what the size increase gives you, It is infusing you with a bit of divine power. (Look at enlarge person). All the Reduce Person does is lower the size back down. (+2 Size Bonus to physical stats +4 to Nat armor, 3/evil DR for 366,000gp is powerful, but only at this level, otherwise it is too expensive.)
The rules support the creation of permanent magical effects.
Divine Favor at 9th level is 72k, no way in the item creation rules to give a bonus to attack and damage. You example is flawed with the bracers of archery because they have other effects (They give a feat and the bonus to hit and damage is dependent on having the feat independent of the item.)
Sometimes spells are cheaper than an associated item, sometimes it is the only way to get an item to do what you want it to do.
Righteous Might gives bonuses above and beyond what the size increase gives you, It is infusing you with a bit of divine power. (Look at enlarge person). All the Reduce Person does is lower the size back down. (+2 Size Bonus to physical stats +4 to Nat armor, 3/evil DR for 366,000gp is powerful, but only at this level, otherwise it is too expensive.)
The rules support the creation of permanent magical effects.
Divine Favor at 9th level is 72k, no way in the item creation rules to give a bonus to attack and damage. You example is flawed with the bracers of archery because they have other effects (They give a feat and the bonus to hit and damage is dependent on having the feat independent of the item.)
Sometimes spells are cheaper than an associated item, sometimes it is the only way to get an item to do what you want it to do.