To solve this problem, we simply need to use dimensional analysis wherein our desired unit would be $/sip. First, we know that the bottle costs $278 per bottle which amounts to 24.5 fl. oz. It was also mentioned that 2 mL of wine is consumed per sip. Also, the conversion of 1 fl. oz. equal to 29.6 mL will also be helpful. The following expression is then used to solve the problem:
$278/24.5 fl. oz. x 1 fl. oz./ 29.6 mL x 2 mL/sip = $ 0.7667/sip
Thus, we have arrived at the answer that one sip costs about $0.7667.