I did this last year, but quite slowly, so I couldn't say exactly what it cost. In many ways, I enjoyed it more than buying and building a boxed set, as it took shape gradually, and I had to make modifications as I went along because of the cost of certain pieces (as others have mentioned above).
I would certainly recommend familiarising yourself with the intructions, as you may find that a piece you went to a lot of trouble to find is not actually seen, and a cheaper colour would have done. For example, the hinges holding the baskets at an angle in front of the shop are sand green, but really any colour will do. Also, I used a mixture of new and used parts and could hardly tell the difference most of the time, so this could save you some money too.
Here are the main modifications I made:
Used 1x2, 1x3, 1x4 and 1x6 sand green bricks but no 1x8 (as discussed already)
Swapped the dark green bricks for dark grey
I didn't use the 1x2 sand green bricks with a groove, but created a brick pattern with 1x1 and 1x2 bricks instead
I didn't want to use blue for the awning, as this would look the same as the Pet Shop, so I tried red and green but ended up with medium blue
Added an extra window to the back of the top floor, as I didn't like the blank wall. This saved a few sand green bricks too
The lime green cherries were hard to find (although I now have some from the city advent calendar) but other colours looked fine
I don't think all my minifigs are an exact match, but they are close enough
I went on to make some further changes, as I didn't like all the white used for the bay windows. I'll show you how it has ended up looking if I can work out how to add an image (it's my first post here).
Nic.