I'm going to work with the current pricing in my market, it's a European country and very competitive in the stone sector, so it can be a little different than the prices you will find in you local market, but the proportions may give you similar results.
In this post I will use the current slab price (2010 price list) for Luna (Compac Quartz colour). Luna from Compac Quartz is similar to other colours in most manufacturers, Silestone has a Blanco Norte, Caeserstone has a 3141 Eggshell.
The current cost for 3 cm thickness slabs in my local market per sqm is around 80-85€ (they usually give you a discount on this price).
One thing that separates granite from quartz is the size of the slab, quartz being a man made stone, or engineered stone, it comes in standard sizes, most manufacturers offer 3000 mm x 1400 mm, which is ideal for kitchen countertops. When we look at granite, well the ideal situation would be a 3000 mm x 1400 mm slab also, however the normal size is over 3000 mm x 1500 mm.
To account for costs, I have chosen the following kitchen countertop. The kitchen countertop should be an L shape 3000 mm (on the long side of the L) and 2000 mm (on the sorter side of the L) long. No doubt that the ideal situation would be a one piece unit, which is impossible to make from quartz engineered stone, but even if we had a slab that big of granite (which is possible), managing such a big and awkward piece of stone in the countertop fabrication plant and all the way to the kitchen counter... is almost impossible. So what is commonly done, it's divided into two pieces, in our case it'll be one with 3000 mm and the other with 1350 mm, counting with a 650 mm width on the countertops all the way around. So we'll be fabricating 2 pieces: one with 3000x650 with front edge polished and with a slight bevel (leaving an unfinished 650 mm, this is where the other piece is going to be fitted in); the second piece will be 1350 mmx650mm with front edge polished and with a slight bevel. We can add two cut outs, one for the oven and another for the sink.
So let's get down to numbers:
1. Quartz Countertop:
- Total cost of raw material: 1 slab 3000x1400 x 80€ = 357 €
2. Granite Countertop
- Total cost of raw material: 1 slab 3200 x 1600 x 35€ = 179,20 €
The production process is very similar to both products, tooling is also very alike, although the consumption of diamond tools are different, the wear on tools is greater on quartz than on granite.
Countertop production cycle
- Cutting the slab : The slab is cut to size with a bridge saw
- Polishing the edges: The front edges are polished and finished according to the project specifications
- Doing the Cut-Outs: The two cut outs for the oven and sink are done manually using tools for that purpose
- Packing, delivery and sometimes installation
To resume this whole issue, I believe granite should in most cases be cheaper than quartz, so if you are looking at price focus on granite countertops.