Cloning the brain itself wouldn't pose any particular problem once you can clone the whole organism. However, making it viable for implantation later would present some unique challenges. The brain has to be stimulated in order to create somatotopic, retinotopic, and tonotopic maps. Olfactory receptor neurons won't send afferent processes to individual glommeruli within the olfactory bulb without odorants present,etc. The point is, an immersive (sim)sensory environment is needed for all but the most basic neuronal development. The flesh is fairly cheap, but creating sensory maps, error correction of motor output, and basic learning will require a fairly sophisticated simsense setup and that just gets you to a brain that can operate on an animalistic level. Learning language skills, reasoning, (un?)ethical decision making will all require a medical facility and some serious time and cost.