Woohoo, nothing against a bow that needs two rounds to grant +20 to one shot ... but!
The first thing I would buy after such bow would be boots of speed, potion of haste or similar things. Perhaps scrolls of haste if I had some level in wizard. Or later the first spell in third level would be haste.
--> Partial Action: Activate True Strike
Full Round Action: Shoot Arrows with the first at +20 ...
All you trade in in respect to "normal" haste (w/o true strike) would be one attack at highest bonus. I would definetly do that against heavy AC guys.
Now imagine the fighter type with power attack 15 ...
True Strike is a spell for wizards (personal) only. Wizards seldom take Power Attack as a feat. Wizards have a bad BAB, and this spell is meant (IMHO) to give the wizard a chance to hit once every two rounds for sure (perhaps with a ray or crossbow or whatever).
Now if you make it available to all classes without taking the Range: personal into account the spell gets a little over the top. Honestly: 1500GM for a +20 bonus to attack ??? I could imagine more than one situation were this would be more than neat.
The same for the spell Shield ... Expeditious Retreat ... Why is there a range: personal instead of range: touch ???
And remember the wizard has to prepare the spell and can cast it only a limited times per day.
The table "pricing of magic items" should always be a GUIDELINE not the ultimate truth. IIRC the title was changed for the same table in T&B in "estimating prices for magic items".
I could handle a true strike item with 1/day or 2/day maybe even 3/day but not at the base price derived from the table in the DMG or T&B.
Just my humble opinion, don't take it personal Dark Dragon.
BYE
[Edit] Typing