You're correct about the average slaveholder having about five to seven slaves. Of course slave ownership didn't make a man wealthy. However, in any case only wealthy men would be concerned about a high tarrif. As long as it was well made and did the job, the common man who needed a plow didn't care where it was made. Just as today, most people only care about a fair price for a good product. You can find something to drive other than a Mercedes or a Ferrari.

When high tarrifs were in effect (early 1830s, 1842-46, and 1861+), they impacted sales of luxury items like pianos, not plows or saws or other small tools. Often taxed items were the same ones which later had to come through the blockade, such as medicines.

Why would small-time Southern farmers raise a clamor over the high price of rum and molasses from the British West Indies when better and cheaper home-grown/home-made local products were available?