1 billion is equal to 1,000 millions. 1 million coins for a rune.....if I spent the 80 million I would need to buy enough runes to expand once I would still have enough coins to expand 20 more times. Immediately. Or every 12 hours. I don't see team lava offering that type of a deal. I could see them offering 1 rune for 10 million...... and I'd love it.
Between my kids and myself we have spent lots on gems, but never to buy missing runes, although especially my daughter has recently been selling off a lot of the 'normal' animals as she has run out of space and not enough runes to expand.
More ways to get runes would be great. It's very much appreciated that they show up in spins (but you need to be lucky enough to get them), and as chapter rewards in story books (though 5 or 10 are a drop in the ocean when you need 70+ to expand). I love the value packs that offer runes, although not when they include snakes... (Value) packs that only offer runes, at a fair price, would probably sell like hot cakes!