Sorry for the delay in getting this post resolved, but have been traveling and haven't had much time to post.
Called the restaurant in question and asked about this, and tax is the correct answer. Bar prices are inclusive of tax and tax is broken out on the invoice in the dining room. I'll chalk it up to miscommunication from the wait staff as to the explanation of a dining room surcharge and I guess a misunderstanding on the price difference from my Father-in-Law since it should have netted out to the same price.
Anyway, it certainly never would have kept either one of us from going back to Palermo Viejo which is where this incident occurred.
Appreciate everyone's ideas-Doug