Of course, like more valuation questions, it really depends. Furthermore, valuation is a highly subjective art and science. That said, most will probably agree that a balcony is considered a nice to have feature for a condo. As for the question on how much value it will add to the unit, I would put it around 1-3% (with some exceptions). A lot depends on:
• The size of the balcony
• Its general usefulness
If the balcony adds a materially big amount of square footage, buyers will obviously perceive more value than a smaller balcony. If the balcony is big but faces another building, the value is naturally less than a big balcony facing the Sound.
If there are two units with an equally good view and one of them comes with a balcony, the value can increase as much as 3% even at the high end. It will be hard to imagine someone paying for more than a 4% premium for a balcony.
In summary, the lowest value blaony is one that has no view and is small (this will yield a small 1% premium, if any).The highest value balcony is the one that is big and has a view which can possibly fetch as much as a 3-4% premium.