From Longman Dictionary of Contemporary EnglishI/you should be so lucky!I/you should be so lucky!spokenPROBABLY used to tell someone that what they want is not likely to happen, especially because it is unreasonable You want three weeks holiday? You should be so lucky! → lucky
Examples from the Corpus
I/you should be so lucky!• Sleep past 6 a.m.? I should be so lucky! 