Sub-subsistence wages? ;-)
It is necessary to keep in mind that "subsistence" is necessarily relative. Subsistence wages are the minimum wages necessary to reproduce the supply of labourers. Furthermore, if the development of industry requires labourers with a minimum standard of education, then subsistence wages must be sufficient to sustain that. This has quite wide implication, it means for example that if industry as a whole requires a minimum level of economic and political stability and higher living standard to operate properly, as modern industry certainly does, then it stands to reason that "subsistence wages" must be sufficient to sustain that.
Thus subsistence level wages shouldn't be interpreted narrowly as some absolute measure of the bare minimum cost of feeding a labourer, if the labourer requires a long education and a stable social environment to be able to perform the work properly, then subsistence wages are whatever it takes to make that happen.
Bill Bartlett Bracknell Tas