Yes, The Maartian, it is not cheap, but if you want vocals that sound realistic, it costs a lot less then hiring singers. I have eight English voices, so I guess I spent even more, but I am happy.
If you want to make vocal harmonies, either for back-vocals in a pop song, or for choirs, Synthesizer V is the best. Here are a few examples I have made over the past year, all 100% Synthesizer V:

Try To Remember
A Nightingale Sang in Berkeley Square
London By Night
Somewhere Over the Rainbow
Their Hearts Were Full of Spring
Can't Help Falling in Love

All of the above were made with the old version of Synthesizer V, but there is a new update with lots of new features, and it is much more capable and faster, so the future examples will sound even better.

By the way, I should mention that another user advised that if you want to quickly use Synthesizer V to realize BIAB automatic harmonies, it is faster if you make the harmonies in RealBand instead of BIAB, because that can print and export the harmonies (either Audio or MIDI) with each harmony line on a separate track, which is the way Synthesizer V needs it. If you are used to BIAB, you can make the song and melody first, and then open it up in RealBand just to get the separated harmonies.