I've always thought the ward spells were too costly - especially when using them stops mana regeneration...

-- Updated and Fixed -- (now with 100% more in-game testing :)

This file reduces the cost of the 'Ward' spells into a linear progression:

WardLesser24->20
WardSteadfast 39->30
WardGreater 56->40

The vanilla costs increase faster than the magnitude, which I find backwards.

I know of only one other mod that attempted to reduce the cost of the ward spells and it did so by reducing the magnitude of the spell negation (thereby reducing the cost). Unfortunately, this made it worthless in combat.

This mod simply sets the no-autocalc flag on six spells and directly modifies their cost. Just in case you're wondering, yes perks and skill level still reduce those costs. In my game it's (5 8 11).

NOTE: The cost on the uesp wiki is the value in the cost field - but the game ignores it until the flag is set, which is why Steadfast appears cheaper than lesser on the wiki, but is greater in-game.

NOTE 2: Once again I was stuck typing in Spell names,... so I've made them group and sort properly:
Ward I - Lesser
Ward II - Steadfast
Ward III - Greater

Update - Alternate file with Expert / Master level wards

The 'optional' file is a replacement for ReducedWardCost.esp

Progression is a little different for this file:
Power: 40 60 85 115 150
Cost: 20 30 40 50 60

The new spell tomes exist, and are added to the 75/100 Restoration lists, but I only checked the crazy restoration specialist at Winterhold and she wasn't selling either.
addSpell formids: xx860010 xx860011
Book formids: xx86000a xx86000b

-- Update 2011-12-27 --
ZeroWardCost added - use instead of 'ReducedWardCost.esp'
As the name implies all 5 ward spells have been set to zero cost.