I don't know where you are getting low maintenance from. You need a saltwater marine environment for them which means regular water changes with RO water and aquarium salt, various test kits to maintain water quality, filtration, flow makers, heaters and decent lighting.
You can't really keep any cleaning critters in the tank either, as the mantis will kill them, so you have to be extra vigilant with algae that the other shrimp snails and crabs would usually take care of for you.
So yeah cool thing to have but its the same startup and running costs as any other saltwater tank.