Hi, I have phped 4.6, but when I log in to shop, it only shows upgrade price for 3.3 to V5.

What is price for 4.6 to 5 ?

http://shop.nusphere.com/customer/home.php?cat=15

The bottom three items are upgrades from version 4 to 5

If you're a customer and have purchased 4.6 and system does not let you purchase upgrade 4.6 -> 5.0 olease contact customer care dept. with this question.
BTW, all customers who purchased 4.6 PRO have 1 year of _F_R_E_E_ upgrades. This covers 5.0 if you purchased less than 1year ago.
All customers who purchased 4.6 ADVANTAGE have 3 years of _F_R_E_E_ upgrades and this for sure covers 5.0 and next versions as well.
So please first check if upgrade is what you really need to purchase.

It doesn't make sense... On the url you posted, upgrading from 3.3 is cheaper than upgrading from 4.6?!?
Where is the logic behind this?

Also - how can we check until what date we are entitled for free upgrades? Is there a page on the CMS that has this info?

Click on 'my orders' link, it has the dates in there - well the purchase dates anyway.

You should contact customer care as dmitri suggests. Perhaps the pricing on the page is out of date (I'm speculating, of course).

That's correct, the inquery about the pricing should be submitted via Contact US form. We will be happy to explain of course