Well, the Revell Lionfish has been the target for some RC-sub conversions but I have never seen one that was fully RC'ed since the hull space inside is way too tiny to be able to fit any available eletronics inside. If you want to, you'd have to go micro!

I don't know what you mean by "cheap" but some WTC's do come at more than a $100, unless you choose to make it yourself. It's a build it or buy it situation!