Can you buy just the slabs from IKEA?

I don't know. They work with a local stone place, and you can go and pick the slab. Just grabbed the price sheet and was told that they sell way more than what they have on display in the store.
For some granites, it says "Color that requires a slab layout."

When we priced counter top for our hall bath, we did not think their deal was good at all.

The best way is to actually go to granite yard pick out the ones you like and compare the price including fabricator's labor charge. In general the promotional pieces are not of desirable selection, they are lower priced pieces to begin with.

Good to know. No clue about counter prices as I'm totally overwhelmed by the choices, but I thought that Cambria was more expensive in general than 79.00 installed.
Their promos for Caesarstone are:
Crema Limestone Honed 2300H and Sandalwood Polished 6263 for 49.00.