Will this give you an idea of how much it will be?
http://www.marbleandgranite.com/stone-slabs/natural-slabs/granite-slabs/taj-mahal-(quartzite)-granite-slab-polished-3cm

Here's a discussion where someone was quoted $7-12k for the Taj Mahal
http://houzz.com/discussions/530701

The price varies quite a bit amongst the granite slabs and depends on the Uniqueness of the stone, source and the distributor , Some granite slabs are very rare to be found.
The distributors categorize their slabs usually into different price levels that doesn't necessary relates to the quality but rather to the above.

I bought two slabs apprx 134x73 of Taj Mahal at $45 per sqft. It's pricey. Way more than Carrera that was $35 per sq ft before fabrication. Our fabricator added $30 per sqft on top of that. It's a super hard stone to cut. But then it's also a really hard stone to damage!

This stone is well worth paying for…it is so far one of my few favourites!!!

Please note- I paid about $150 per square foot for my beautiful honed Taj Mahal countertops installed 3 weeks ago thinking I was getting something gorgeous yet "hard as granite" to stand up to my young family. I am sorry to say the slightest graze with metal (and I mean slightest, ie: a staple on a piece of paper going across or an eraser-less pencil glancing the surface...) leaves silvery scratches!!!! Waiting to hear from fabricator what the deal is....needless to say I am horrified and very worried.

What happened?

I just got quoted 185$/sqft for leathered taj mahal.

I heard that the polished was more prone. There is so much conflicting information out there.

We have Taj Mahal polished and have never had a problem like this. Ever. Our other countertop is this really nice reclaimed wood and I regret it. Wish I would have done the Taj Mahal throughout.

Please note there are many fabricators importing slabs of granite /quartzite and the quality differs therefore you might see some differences.

Good quality quartzite like Taj Mahal should be hard and resistant to scratches , some superficial marks if any can be polished off cleaning, polishing products.