OP here

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In defense of our friend who ordered the lobster, yes we *did* say we were treating. My DH & I assumed - and yes, I know what assume makes...an "***" out of "u" & "me"

- that "market price" would mean not that much more than the most expensive item delineated on the menu, the $75+ Porterhouse. Our friend does not know how much her entree cost & I am sure that she would be greatly embarassed if she did know - I do not intend to ever tell her. She & her DH have had some bad luck lately & they deserved a treat. I have no regrets about taking them out.
My whole point was to let others know that they should make sure they *ask* when confronted by the words "market price" on a restaurant's menu. Don't assume that the particular menu item in question will be priced somewhere in line along with the prices of the other items.
Plus the entire service rendered was somewhat lacking.
I will make sure in the future if I am ever 'treated' to a dinner out, that I will never order anything that says 'market price'. I wouldn't want my host to have a credit card heart attack

. Lesson learned.
agnes!