I don't see why people think Permanancy should be changed. Sure, it costs some XP - but no gold. And while it can be dispelled, the fact that you can extend a spell way past it's usual duration is worth something - even if you only keep it for 5 or 6 encounters before it drops.
I mean, 500 XP isn't really all that much - there are many spells that require XP of around that value, and people never complain about that. And those spells only last for one casting. Spells cast on yourself can't even be dispelled unless the caster is of a higher level that you were when you cast Permanancy. That eliminates most monsters, and many NPCs. What DM sends wizards of higher levels at his party every encounter? That's a bit wacky. So you will usually get some benefit from Permanancy.
The only spells that are pricey XP-wise are the powerful spells you cast on items. They make near-instant magic items at no gold cost - and are also usually powerful spells in their own right. Sure, you might not need them very often, but they do come in handy in a pinch.
Perrmanant Teleportation Circle is a great way to move an army - clear across the world! It takes only 2 rounds plus 10 minutes (for casting Teleportation Circle) to set that up. How much would that be worth in gold, and how long would that take to do? Let's see, it would be a Wonderous Item. The first value is the material cost - there's a Gp cost to the spell (1000gp) so that value will be 100,000 Gp (since the item will be continous). There's no XP cost for Teleportation Circle, so that is 0. It's a use-activated/continous effect so that's 9 (spell level) x 17 (minimum caster level) x 2000 x 1.5 (since Teleportaion Circle's duration is measured by 10 mins/level) which equals 459,000 Gp. Added to our previous total we get 559,000 Gp. Last, the item takes up no body slots, so the final total is multiplied by 2 - for a grand total of 1,118,000 Gp. That means the item will cost 559,000 Gp to make and 44720 XP. Oh, and it will take 3 years (or at least, Earth years) and 23 days.
But Permanancy does it in 10 minutes at the cost of 4500 XP. Not a bad deal. Of course, if a player were to want to make an item out of Teleportation Circle, I would likely lower the costs from what the book says - but Permanancy might still be the way to go.
To make the XP cost of the item the same as Permanancy, the item would have to cost no more than 112,500 Gp base - and I'm not sure that's high enough for an item with a continous 9th level spell. It would really depend on how the players intended to use it... But you can quickly see that to make items (at the same XP cost) for many Permanant spells the base price of those items would be unusually low.
Code:
Spell Level XP Item Cost
Phase door 15th 3,500 XP 87500 Gp
Prismatic sphere 17th 4,500 XP 112500 Gp
Prismatic wall 16th 4,000 XP 100000 Gp
Shrink item 11th 1,500 XP 37500 Gp
Solid fog 12th 2,000 XP 50000 Gp
Stinking cloud 11th 1,500 XP 37500 Gp
Symbol of death 16th 4,000 XP 100000 Gp
Symbol of fear 14th 3,000 XP 75000 Gp
Symbol of insanity 16th 4,000 XP 100000 Gp
Symbol of pain 13th 2,500 XP 62500 Gp
Symbol of persuasion 14th 3,000 XP 75000 Gp
Symbol of sleep 16th 4,000 XP 100000 Gp
Symbol of stunning 15th 3,500 XP 87500 Gp
Symbol of weakness 15th 3,500 XP 87500 Gp
Teleportation circle 17th 4,500 XP 112500 Gp
Wall of fire 12th 2,000 XP 50000 Gp
Wall of force 13th 2,500 XP 62500 Gp
Web 10th 1,000 XP 25000 Gp
In the end, I don't think it's a bad tradeoff to have Permanancy take 3 rounds cost 0 Gp some XP and be dispellable, while items could cost significant Gp and XP - and take weeks (or more!) of game time.
