Nearly 60% of Los Angeles area small-business owners forecast increasing sales for 1987, according to a study of 7,000 businesses conducted by Arthur Andersen & Co. Although insurance and other costs have risen dramatically, about 41% of the owners said profit will remain the same and 38% expected improved profit. Nearly 85% reported that insurance premiums had risen between 50% and 100% during the past year, with 34% reporting premiums up more than 200%. Most of those surveyed said they are absorbing the costs and reducing the amount of their coverage. More than 60% had been contacted about a merger or buyout in the last year, the study said.