Yes from a hardware point of view, custom look-up tables are much cheaper than multipliers. On the other hand, the point seems to be to utilize the LUTs of FPGA

Yes from a hardware point of view, custom look-up tables are much cheaper than multipliers. On the other hand, the point seems to be to utilize the LUTs of FPGAs which are not very power-efficient because they also need to be fully programmable. In theory you could hard-code the weights of a network into an ASIC, or even just a new generic building block that is cheaper than multiplication. This would then be near impossible to beat, if anybody can be bothered to optimize for this architecture.