Are you talking about the 032 pattern " Texas Jack " as they currently call it, or the 087 pattern " Medium Texas jack " ?
Either way I would guess because the half whittler seems to sell more, which would be evidenced by the fact that it has more cover options. ( the 032 only has one option, and the 087 only two )
Think about Buck knives, the 110 has more material and should cost more but the 112 and little 55 do because they don't sell nearly as much of them as they do the 110.