Respeccing Glyphs

Glyphs are going to be a not-inconsiderable and constant drain of gold/resources on every serious raider.
Why do I say this? Because of the fact that while some glyphs are good for solo play - grinding, daily quests, etc. - some are better for raiding. So a serious raider will want to switch back and forth between the glyphs.

Consider for example Glyph of Frostbolt. This will be a must-have glyph for a raiding frost mage, as the slow component of Frostbolt is (almost?) never needed in raids. However the +5% damage is invaluable.
However as soon as you finish the raid and want to go do your dailies, what do you do? If you leave it on you'll lose ability to kite the mobs, a core feature of playing a frost mage. We don't want to get hit on by the mobs, that's for fire mages to endure! ;)

So what can be done? Nothing much in my opinion. Do your homework, select which glyphs you'll be replacing regularly and which will stay and get a large stock of the ones you'll be switching. I'm hoping the extra cost of switching glyphs will be offset by the reduced cost of using less mana and health pots during raids, but we'll just have to wait and see.

As for leveling 70-80 and doing instances - if you're worrying about glyphs while leveling, you're either waaay more hard-core than me or over-optimizing. Consider the fact that a shadow-priest can be a healer for an instance run while leveling - do you really need to tweak your glyphs?

For leveling 70-80 my current plan is to go as Frost on my mage. My prefered glyphs will be: Glyph of Water Elemental, Glyph of Mage Armor and either Glyph of Evocation or Glyph of Mana Gem. I might switch to Glyph of Frostfire at 75 - I'll have to wait and see :)

For my other characters I still haven't taken a look but I will have time as I really won't have time to level all of my chars at first.