How can you say, beer costed 27 dollors? If it costed 27 dollos, why did the shopkeeper charge 25 dollors only???

Problem:  (Shopkeeper's price = 25)   !=  (Three guy's beer's value = 27 :: as thought by Ratobhale which is wrong)

Money is not lost anywhere.

Initial Scenario:

$10 x 3 buyers = $30  TOTAL

Final Scenario:

($ 1 per buyer) x 3 buyers  +  $2 (Assistant) + $25 (at Shop OR with three person as 'beer') = $30 TOTAL

Total Money at : Initial Scenario = Final Scenario

DONT THINK IN COMPLEX WAY!

Problem in Intial Question: "After they got back 3 dollars, their cost was 9 dollars a drink. So 9 times 3 is 27 ..."  IS WRONG.! Actually, 27 is NOT 'total cost' but it is 'total cost + asssistant's 2 dollors'. Total cost of beer is therefore 27 - 2 = 25 (NOT 27) which means 25/3 = 8.6666 dollors per head.  [if 27 were the total cost as cited, then "27 (now beer value) + 2(Money) + 3(Money)" = 32, ... from where came 2 dollors now??- would be the scenario, which is wrong...].. But we can not say 27 (beer value)..

SO, (8.6666 x 3 + 2) is what the three guys paid after they got 3 dollors refund. Therefore, 8.666x 3 + 2 + 3 = 30.