The amazon UK is currently selling the Ice Age 1-3 blu ray collection for only around $18.50 delivered.
Amazon's link :
http://www.amazon.co.uk/Ice-Age-1-3-Collection-Blu-ray/dp/B0…
They are also selling the Ice Age 1-3 dvd collection for $15 dollars delivered.
Amazon's link
http://www.amazon.co.uk/gp/product/B002JPKSBK/ref=ox_sc_act_…
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CamelCamelCamel 
Keepa.
The same thing happened to me with Die Hard.
I bought Die Hard trilogy back in like 2005 thinking they'd never do another one, it's been too long.. Then they made 4.0. I bought the Die Hard Quadrilogy (even though I hated 4.0) just so I could get rid of the trilogy and look less stupid. And now 5… I'm not buying that, because that would only guarantee they do a 6.
Fool me once, shame on you. Fool me twice, shame on me.
I own a few other "trilogy" box sets btw..
Pretty sure i saw this at kmart for the same price if not cheaper on the weekend. If anyone is visiting one today it might be worth a look.
For 3 movies it's a good price. Only problem is, it's not a complete collection. There's a 4th movie, and I doubt that will be the last either.
I haven't seen 4, but I've seen 1-3 and I loved the first movie. It's one of my favorite animated movies. But the rest were kind of meh. I don't remember much of the second movie apart from the mammoth dude meeting a lady mammoth.
tried the link but it wouldn't ship to my AU address.
Just a note: this isn't the "complete collection" as it says on the cover, there are now FOUR movies, and this set doesn't have the fourth one.
Here is the complete set with all four movies:
http://www.amazon.co.uk/s/ref=nb_sb_noss_1?url=search-alias%…
However, it is significantly more expensive than this deal.