Neither study addresses compliance costs!Both studies address the growth implications of taxation and government spending on the economy. Their conclusions essentially say that for every dollar collected and spent by the government the economy could have generated about two dollars in additional growth if the money were left in the private sector. That is not compliance cost (or any cost, for that matter) it is lost opportunity because the government collects and spends tax dollars. It has nothing to do with the price of goods, or whether those taxes are collected from income or consumption.
Now, don't get me wrong: increasing growth potential is good. Just don't confuse it with reducing prices.
The Payne study (a compilation actually) does essentially the same thing. MOST of it's so-called "costs" are really lost growth potential, not costs that help reduce prices if eliminated.