Obviously the pump isn't in the picture here, but, other than that, this is the entirety of my RIMS setup. The cost of the major components (Heater, PID, SSR, tri-clover stuff) was around $250, so say $275-300 with the box and GFCI plug/switch.
Compare to the Tower kit that still needs your own burner at nearly $600
Wasn't too complicated to get put together. Plus, it's more or less a stand alone unit that can be put on any mash tun fairly easily.
As for solar powered RIMS... I'd doubt you could pull the power needed with any reasonable kind of solar system.