So, how do you pronounce DureAce?

Dura (think the word durable) and Ace like in a deck of cards. We blend the words together at my shop as a joke and call it Durace with an accent on the e making it sounds Italian haha

dura-cell

but with ace like in cards

Dura-ace

Durrache...with a spanish accent.

most bike shops I've been in don't care how you pronounce it :)

So, how do you pronounce DureAce?
Eks-pen-siv

Or, if you're Shimano or the LBS:

Ka Ching!

Lucky for you there is a phoenetic alphabet here in Japan

From Official sources its pronounced:

duu-ra ace (the script is a long A sound in ace)

TakmanJapan

It's actually spelled Dura Ace which is also how it's pronounced. If you spell it correctly in here, you'll get a little pop-up logo at the end of your post that says, "Products mentioned in this post" or some such. And it's a link to the mfg.