The estimates you've been given sound correct. If you want to know exactly how much they'll charge you, start the booking process but don't finish it. I just did this the other day when trying to help my non-status brother search for flights.

Find an itin that you'd like, click on the "purchase now" button, then on the next page enter a short fake name for a "new traveler", such as "Li Oh" to save time, make up a birthdate/gender, skip the contact info, then go to "choose your seats". Hovering over the different E+ seats will reveal the price.

The payment info is the last thing that's entered after choosing seats, so you don't need to worry about accidentally making a booking. Just close the seatmap webpage or hit the "back" button on your browser.