I am no expert, but I've done a few rehabs.  When I walk houses I try to think of what it would cost for various things.  I am usually off, sometimes way off.  I thought it would be helpful to some newer people to post real world examples of prices.

Example: house in the 150K range.  I typically wouldn't put granite in a house like this but I had to replace the counters anyway so I went for it.   2 small bathrooms that had one sink each.  

My thought- By measuring you can come up with your square footage pretty easily in a bathroom like this- then just multiply that by your SQ FT price.  In my example, the counters were 64.5 in X 22.5in  and 59.75in  X  22.5in.  its about a total of 20 sq ft.

What did I forget??

Cost of white oval bathroom sink & cutout was $75 each (kitchen sink is $150)

Calculating the 3 in (I think that is the size) backsplash that goes around the permiter.  That (according to the quote) added approx 5 SQ FT.

Waste- my guy charges very little for waste if I use the basic colors that he uses all the time.  In this case he added a few sq ft for waste.  You need to check because some places will make you pay for a whole slab.

Total he charged me for was 28 sq ft.  I used St Cecilia (sp?), which is considered a base level for most places.  My guy charges me $28/sq ft installed plus the sinks shown above.  NOTE: from what I've seen these are pretty good prices per SQ FT on granite.

$28 x 28 sq ft= 784

2 sinks= 150

total $934