In Greek, it would have been spelled -αι "ai" and pronounced -/aj/ or -/aʲ/ (I think there is debate about this subtle distinction, which does not matter for us here: it sounds like English eye).
In classical Latin, it would have been pronounced the same as in Greek, -/aj/ or -/aʲ/. Almost all Greek words we have came to us through Latin.
In the older international pronunciation of Latin, which was based on the Romance languages but used throughout Europe, it is -/eː/ or -/eɪ/ or something similar (like English say).
English, however, went through several vowel shifts, part of which was that vowels pronounced like /e/ came to be pronounced like /i/. So the pronunciation of the English word written as see was once like modern say, but has shifted to its modern pronunciation, /siː/. Spelling changed more slowly than pronunciation, or not at all.
The English also applied this shift to words of Latin and Greek origin, because such words on -ae were often or normally pronounced /e/ (modern English say) before the vowel shifts, as I said above. It was often spelled -e instead of -ae in manuscripts, but also even in print, at least until the humanists got their way of restoring the classical spelling -ae.
That is why the traditional English pronunciation of -ae in Latin or Greek words has been like /i/ for a long time. If you want to be conventional, I would pronounce it this way, although other pronunciations are not necessarily stupid: they may correspond to different points of view.