After you posted this, I used the Mousesaver's link to UT, and I get a price of $458.95 for 10 day non-expiring (without park hopper). Dreams Unlimited comes to $434.35, which includes the tax and shipping they ad. Am I missing something?
OK, so I gess I'm a little slow. ;-) I see now that the low prices are only available through a link in the Mousesavers newsletter. I subscribed, but will get it too late for the price increase. Can someone please post the link here? Thanks.
From what I can tell, you aren't comparing the same ticket.
The ticket at UT listed for $458.95 is a 10 day no-expiration water park fun and more.
The ticket at Dreams listed for $434.35 is a 10 day no-expiration ticket. It does not appear to be the water park fun and more.
Unless I didn't see the same tickets you saw, which is possible too! Comparing prices on disney tickets is enough to make my head spin! There are too many different types!

We are headed to WDW for our first trip in september and it looks like I'd better order the tickets ASAP.