 This tactic proved highly successful , with Sinclair announcing by March 1982 that it had sold 250 @,@ 000 ZX81s worldwide . When sales fell in the wake of the launch of its successor , the ZX Spectrum , Sinclair reduced the price of the pre @-@ assembled version to £ 49 @.@ 95 in May 1982 . It was cut by another £ 10 the following April . Despite the increased competition from much more capable computers , the ZX81 was still shipping in excess of 30 @,@ 000 units a month even as late as July 1983 , more than two years after it had been launched . By that time , according to Sinclair Research , over 1 @.@ 5 million ZX81s had been sold . 
