As 318 blocks are everywhere and a 360 crank, used is ethier free from your destroyed donor or cheaply had, the build isn't as expensive as other builds and provides a different angle on doing something different.
I would not do this build myself. But someone else might have such parts hanging around doing nothing. They may have not thought about it or never did any research on how it could work. BJR did and showed how it can work. The real extra cost is in crank machining and if stock pistons are used, valve relief cutting. Which is cheaper than custom pistons that are on the shelf.
Speed-o-motive has kits for this build. Expensive.
Like I said, this is not what I would do, but I also have complete engines ready to go for building. I would not try and create this combo when I have parts ready (For building or not) and complete engines.
This is just another angle on building from spare parts and something you want to do. Want is also a thing that doesn't consider or care about cost.