Having just purchased one (I received it yesterday) I did a bunch of price-searching on the web, but couldn't find anything different from what you've found. The prices must be very carefully controlled by ACR Electronics since nobody seems to go below a certain price - though lots are trying to sell for much more - buyer beware.

Referring to the unit with the internal GPS:

The TerraFix and AeroFix are $650, with a $75 rebate from ACR, so the final price is $575.

The AquaFix is available for $575, with a $65 value RapidDitch Express bag, but no $75 rebate.

I didn't need the bag and prefered the green or black case, so I focused on the TerraFix or AeroFix. I ended up buying the AeroFx - with the black case - from http://www.aeromedix.com, if nothing else because they've done very well by me with my Ritter knife a and light purchases. The only problem with buying the AeroFix is that the external GPS cord that comes with it has bare wire ends rather than the serial connector. But then again I don't really need to use an external GPS, so that is no big loss. At some time I may see if I can buy the connector with the serial connector just to be safe.

By the way, it does take some time to register the PLB with NOAA, apply for the rebate with ACR, and complete the warranty info with ACR. I wish the rebate web site would have told me that I didn't need to submit warranty info also since they collect almost the same info, but it didn't. I will say that the NOAA PLB registration site is very nicely done. I especially like that I can go back anytime and update/modify the contact information. That helps ensure that that info is up-to-date, which means as much to me as it does to NOAA.

Ken K.