http://www.d20pfsrd.com/magic/all-spells/t/true-strike
Duration see text1 round duration spells have Duration 1 round. Hence True Strike is not a 1 round duration spell. In fact, the text makes it pretty clear that the duration lasts until you first attack. So even if you made it into a permanent magical item, it'd work until the first time you attack, then you may as well throw it out.
Your next single attack roll (if it is made before the end of the next round) gains a +20 insight bonus.
You people seem to be missing the fact that the prerequisite for Forge Ring is a CL of 7. Hence, you HAVE to be AT LEAST 7th level to make a ring, no matter what the level of the spell.
you seem to have missed the point that this was already discussed only a few comments above yours
But the GM has every right to up the price on such an item as 2,000GP for permanent enlarge is far too low. I would make it cost more than a permanency spell (probably around 10,000GP) and probably take a command word to activate. There are several items that you have to activate in order to get enlarge person that cost much more than 10,000GP. Also, you get the benefit of the ring not losing your permanent enlarge person from dispel magic as a permanency spell would, so it should cost more than a permanency spell. If your GM lets make a ring of constant enlarge person for 2,000GP, see if he will let you make a ring of constant true strike for 2,000GP as well.
Edit: To answer the necro post, nothing is stopping you from buying an actual large weapon to use while enlarged that won't shrink when leaving your possession.
True strikes an instant spell, it can't be made permanent. You also mentioned that true strikes duration is one round, but that's not actually true. Its duration says to see text, where it describes an instant effect with a trigger. The trigger has a time limit, but the effect is instant. Basically its an instant spell with a time limit, not a duration. This is why you can't make a ring of constant true strike no matter how much gold you have. You can make an item with unlimited uses of true strike, but it will not be constant and it will require activation
Example: Rob's cleric wants to create a heavy mace with a continuous true strike ability, granting its wielder a +20 insight bonus on attack rolls. The formula for a continuous spell effect is spell level × caster level × 2,000 gp, for a total of 2,000 gp (spell level 1, caster level 1). Jessica, the GM, points out that a +5 enhancement bonus on a weapon costs 50,000 gp, and the +20 bonus from true strike is much better than the +5 bonus from standard weapon enhancement, and suggests a price of 200,000 gp for the mace. Rob agrees that using the formula in this way is unreasonable and decides to craft a +1 heavy mace using the standard weapon pricing rules instead.
it would actually be much worse. By the standard rule it would cost 800,000gp, but paizo doesnt address weapons above a +5 enhancement bonus. 3.5 did though and they added an epic factor for such weapons that multiplied the cost a great deal. A +20 weapon in 3.5 cost 8 million gp
How much does it cost to have an NPC put a permanent reduce person on you? I'm coming up with 48,500gp? Reduce person lvl 1 claims lvl1 = 1x1x1000=1000gp permanency spell lvl 5 caster lvl 9 = (5x9)x1000 = 45,000 plus 2,500 material components?
you're responding to a post that's 4 years old so you're unlikely to get a response from any of the orignal posters. That being said, what you have looks to be correct.
A few corrections, the same caster needs to cast both spells for permancey, but on the plus side it is multiplied by 10gp, not the 1000 you have used. So 9 x 1 x 10 (90gp) for the reduce, another 450 for the permanencey, and then the 2,500 for materials. So 3,040gp total.