Exegesis:

aganaktountes (cf. 10.14) ‘indignant,’ ‘angry.’ The Greek verbal phrase ēsan … aganaktountes ‘were … angry’ must be given some sense such as Revised Standard Version gives it, ‘were saying indignantly.’

pros heautous (cf. 9.10; 10.26; 11.31; 12.7; 16.3) literally ‘to themselves,’ meaning ‘to one another,’ ‘among themselves,’ as in the other passages where the phrase occurs. Black suggests this represents the Aramaic ethical dative, meaning ‘some were indeed vexed.’

eis ti (15.34) ‘for what reason?,’ ‘for what purpose?,’ ‘why?.’

hē apōleia (only here in Mark) ‘destruction,’ ‘waste.’

gegonen ‘has happened,’ ‘took place.’ Literally the question reads: ‘For what purpose did this waste of the ointment occur?’

Translation:

To themselves must be understood as reciprocal, not reflexive, e.g. ‘they were saying to each other.’

Indignantly must often be treated as a separate verb expression, e.g. ‘some of the people there were angry and they said to each other.’

Wasted may be translatable in terms of (1) discard, i.e. ‘thrown away’ or ‘used for no good purpose,’ or (2) failure to use properly, e.g. ‘not used for a good purpose.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .