According to the Chinese specialised catalogue (Chan), the typo and litho versions of the ½ and 1 Cent stamps can be distinguished by the presence or absence of a dot in the border above the SH of SHANGHAI

Chan rates the ½ and 1 Cent mint litho at around $US2, and typo at around $US0.20, each - but as Nigel says, you need to discount for the condition of your stamps.