So, you don't think that that cost to produce has an affect on the supply of a product?
What I said was that it won't be a 1:1 reduction because in addition to cost, supply and demand affects price too. Prices in some sectors are more affected by cost and some less. Service industries are more affected by cost, but commodities are especially a good example of less.
I remember a time when many oil rigs in the US were shut down because the cost to get oil out of the ground exceeded the price they could get for it. Now, oil companies are making HUGE profits. Yet the production costs haven't changed proportionally with price.
I presume sales tax will be levied on commodities as well, and Exxon not having to pay corporate income tax (I'm not sure when it's said and done that they pay all that much anyway) won't affect the price I pay at the pump much at all.
Supporting a national sales tax has both ideological and practical reasons. If you earn the kind of income where a national sales tax makes your bottom line better, that's just practical. You should support it. But supporting it otherwise is then purely ideological and sometimes that's just folly.