We just booked a wishes cruise for May. The total with tax was $140.84, of course that doesn't include a gratuity. We leave from the WL, but I think you may be able to book from the GF. As far as I know, they run them every night.
We are booked for one in May - would have left from Contemporary as that is where we are staying, but I commented on having PS at WCC and she said that they could pick us up from WL and will deliver us to Contemporary when it's done.
We took a Wishes Cruise from WL on Easter night and it was $150 and I tipped the captain $20. It was about 1 hour and a half long and so very wonderful. The nice thing about going from WL is you get more of a boat ride than if you were right by the MK to start with. She took us from the WL down to the area by the Contemporary and Poly where we saw the Electric Water Pagent. Then we took a drive over to watch Wishes. It was soooo magical.