Enhancements of Shields as Weapons

[Bobbystopholes]

I know that the Enhancements to Shields for AC can't be used as enhancements for weapons, but the DMG says you can add weapon enhancements to shields for use as weapons.

So, what would a +1 AC, +1 attack lg. steel shield cost?

Scenario 1:
170 (MW Shield)+1000 (AC Enhancement)+2000 (Weapon Enhancement)=3170gp

Scenario 2:
170 (MW Shield)+1000 (AC Enhancement)+3000 (Weapon Enhancement at Cost of 2nd AC Enhancement)=4170gp

Scenario 3:
170 (MW Shield)+1000 (AC Enhancement)+7000 (Weapon Enhancement at Cost of 2nd Weapon Enhancement)=8170gp

Scenario 4:
I'm a horrible mathemetician

I am leaning towards Scenario 2, but I was wanting to know if there is an actually rule that I didn't read in the DMG.

 

[reapersaurus]

funny enough, this was JUST covered. (on page 8, though)
i really wish the search function was enabled.

http://www.enworld.org/messageboards/showthread.php?s=&threadid=10275

In that thread, it was still not explained to my satisfaction why a bashing shield would be unique in the whole game to not benefit from a +1 weapon enchantment, OR count as a +1 weapon for further enchantment purposes...

edit - oh, it's the first method, as i understand.

 

[Bobbystopholes]

Thanks reapersaurus. I wish the search was enabled too. I appreciate it!