At the MacWorld Expo in Tokyo next week, Apple Computer Inc will add new low-end and mid-range Macs that will be among the cheapest yet, MacWeek reports. It says they will start at $1,390 for a Color Classic 4/80. A Mac LC III with 4Mb and 80Mb disk will be $1,380, $1,500 with 160Mb. A Centris 610 will be $1,860 with 4Mb and 80Mb disk, $2,960 with 230Mb, on-board Ethernet and the internal AppleCD 300i CD-ROM drive; Centris 650, priced from $2,700 to $4,380 with 8Mb and a 500Mb drive. The Quadra 800 will cost from $4,680 with 8Mb and 230Mb disk, to $6,400 with 8Mb and 1Gb.