For a 100-square-foot room, plaster walls cost on average $1,920, although it may cost as little as $640 or as much as $3,200. And for an 8-foot ceiling, plaster ceilings cost on average $600, with a low cost of $390 and a high cost of $800. For both plaster walls and ceilings, the total project cost varies according to the type of plaster ...Web