These are the cheapest reliable CR2032 batteries I could find.
I'm aware you can get cheap batteries from China. I literally have a drawer full of them. But for my purposes I can't risk a battery leak as I will be using them in my dive computers.
Comparison (price beat with these mobs for extra savings)
Masters $13.90 (beat by 10%): https://www.masters.com.au/product/900053382/Energizer-Energ…
Officeworks $11.97 (beat by 5%): http://www.officeworks.com.au/shop/officeworks/energizer-3v-…
FWIW, I've never seen a 2032 or a 2016 leak, I guess they are too well sealed for that, and I've seen quite a lot, changing motherboard cells. Short life on cheap ones maybe, but that's a different concern.