If you already have maintenance, it is $195 ($295 Xstream) for an additional year. If you do not have maintenance yet it is $295 ($395 xstream). I am  not sure how they treat the "30 days of free maintenance included" if you have those, but I would try and extend for $195/$295. Might work.
In any case if you get any form of 1 year maintenance now you get 8.5 and 9 without additional cost. I am now in my second year of maintenance and that's how it worked for 7.5, 8 and 8.5 and according to the email that has not changed. It is an excellent deal in my opinion and now it got even better (i.e. $100 less). I will extend my maintenance for another year in the Fall.

Ciao
TD