아깝다 means "so sorry or bad".. ^^ , your mom promised to give you some allowance if you get 90 point in your exam. but you got 89 point! In this situation you can use "너무 아까웠어(요)" and here is another example in other meaning. you see something kind of precious, valuable. but you had to consume for some reason or broke out by your mistake! Also, in this situation you can use "너무 아까웠어(요)" ^^

Apparently, it means both, but "waste" as in "too worthy to give up or be used that way", so I guess that fits with "precious/dear". This is where a native speaker is very valuable. :) http://dic.daum.net/word/view.do?wordid=kew000046713&q=%EC%95%84%EA%B9%9D%EB%8B%A4

Doesn't 아깝다 mean something like "A pitty, or "waste" (like in "such a waste") So the sentence would mean: "That was such a waste"

I think 아까웠어요 is from the verb 아깝다 (to be precious, dear, valuable). The past tense is 아까웠어요. So I think that means: It was very precious.