That is what I thought as well. Take a look at my teardown of the shoe in the H series repair thread. Ir contains a PCB with masses of filtering and a 'charge complete' detection circuit. The video output and power input are both transient protected.
I was going to build a Hot Shoe myself using my 3D printer. This was out of desperation due to the difficulty in finding one in Europe.
The cost in time to make a neat solution was going to be far greater than the retail price but I could not get my hands on one ! The USA price is $50 each. For a FLIR accessory that is surprisingly cheap. Take a look at the FLIR power supply prices.... crazy expensive for what they are.
I was so pleased to find these Hot Shoes. I did a deal with a FLIR agent to buy them plus a load of other FLIR accessories that appealed to me.
I also have the FLIR MS224 and saw that a chap has created a 3D 'Hot Shoe' for that model. FLIR never made such available for the MS/PS series
The chap is asking quite a high price for the custom shoe but then it likely took him a long time to design with all its complex curves etc.
Fraser