Could this be used in reverse? I'm looking to be able to switch one source between two displays (PJ and HDTV) but some of the solutions are seemingly pretty pricey
Unlikely - a Switch uses both Receiver (Input) and Transmitter (Output) sockets/chips so cant normally be wired in reverse.
There are lots of low cost HDMI Splitters (Distribution Amps) on the market - though be warned the compatibility (or lack of) with a wide range of kit and maximum cable run lengths (Input + Output) makes for a lot of hair pulling.