If I remember correctly when I purchased Navionics at the beginning of the year it was £40 odd.
My new rib already had the iPad mount and a T-Box with battery which is about 199 dollars, it works via wifi and displays the sonar on Navionics as a split screen.
I used it this weekend without any problems however you do have to connect to the wifi on the T-Box it seems every time you use the boat so it's not just jump in and switch it on.
The other thing I found was the iPad locked the screen after a while which was annoying but I'm sure you and sort this in settings?
The transducer is fitted in the bilge in a linseed oil filled chamber.
As expected the iPad was easy to view because of its size but not easy to see the screen because of the sunlight reflections. Need to investigate anti glare screen protectors/sunglasses...
The transducer picked up the depth fine at 30knots where my Raymarine doesn't prob due to where it's fitted.
The overall package is quite cool. The iPad got a soaking all weekend without any problems, however I did find that I kept on having to remove it and lock it away every time we left the boat on a public pontoon.
The T-Box also works with its own app called sonar phone which you can download for free and run the demo. I feel the Raymarine wifish will be much better although I don't think you can use it as a split screen with Navionics? However as its an app they could update that at anytime but I doubt it as Navionics is selling the T-Box. Overall I missed the dragon fly 7 screen and sonar display.
For me I'm going to fit my dragonfly 7 on both my ribs and use the iPad as back up.
I also saw the dragonfly pro 7 at the weekend and I wish I had that one instead of my 7 as the pro is wifi....
I'm still going to incorporate the iPad into my cabin rib build