 Pricing was central to the marketing strategy , as it had been through Sinclair 's career . The ZX81 had been designed to meet a £ 70 price point and was launched at a price of £ 69 @.@ 95 ( built ) or £ 49 @.@ 95 ( kit ) . One Sinclair brochure presented a side @-@ by @-@ side comparison of the ZX81 with the four machines that Sinclair considered its main rivals – the Acorn Atom , Apple II Plus , Commodore PET and TRS @-@ 80 . The comparison highlighted the vast differences in cost , from £ 630 in the case of the Apple II Plus to just £ 70 for the ZX81 , though even by Sinclair 's own comparison the Apple was by far the more capable machine . 
