Don't see it on both my surface rt or my windows 8 pc. Both have 8.1 preview installed. How come? Anyone know how to get this working? I thought it was suppose to have an option in the display section that lets you search for networked displays?
Not sure about the cheapest, but honestly, it's probably not a good idea to go with cheapest anyway. The key is to go for one that's been well-supported and received frequent firmware updates, as each firmware update improves compatibility.
Example, the Rocketfish Miracast dongle didn't previously work with 8.1, and in its 2.0 firmware update it now does. I would say the safest one that people have had the most success with is the Netgear PTV3000. Both it and the Rocketfish one I've tried personally and both seem to be working right now, though I did have display corruption (I assume due to signal dropouts) one time on the Rocketfish one.
Sorry, since my first post in this thread, I found out that it does not yet work with the Surface RT, because Nvidia's Tegra 3 drivers don't support it yet.
I can only confirm that it definitely works with a Surface Pro and that's what I was referring to with my more recent posts, I forgot that this thread was in the Surface RT forum.
For more details on Miracast requirements, there's a good article at WithinWindows.