how much condo insurance

It is build out cost. $250-500 per sq ft depending on finishes.

well, i'm at the low end. i have sponsor finishes plus upgraded upgraded appliances

Guessing min $300-350 unless you are using Chubb who will be higher. You can negotiate this via brokers.

Depends whether you have a stated insurance value that is the maximum which the insurance company would pay or if you have replacement value with no cap on $$ insurance company would pay to rebuild. (Of course for major rebuild might have to use an insurance adjusted to deal with the insurance company.
Basically the insured value has nothing to do with the market value of the apartment. You could have a crummy little 1 BR apartment with a beautiful terrace and perfect view of Central Park that theoretically could sell for $3mm, but the Insured value would only gave to do with interior fixtures/furnishings etc. nowhere even close to 20% of market value of apartment

In general, people buy too little liability cover and too much contents cover. Imagine that your washer hose comes loose while you are away, flooding your apartment floor and three below you, floor to ceiling and the walls. You could easily have well over $1m of liability while your own costs are only $25k for new floors and rugs. The cost of liability is usually $150 per million, so it's cheap to buy. Also take the highest deductible, as this reduces costs significantly. Do you really want to bother with the insurer for a $2000 claim?

the answer is for almost anything is more umbrella policy. i just doubled it

In my experience, Chubb will come and inspect your apartment and jack up your coverage if you have a replacement policy, and will not listen to debates about rebuilding costs (even in my case after I had just gut renovated to the bare walls and floors for much less). Some insurers separate personal property and dwelling coverage, others do not. Some companies set personal property limits as a percent of dwelling coverage regardless. But even for your personal property, add up what it would cost to replace everything in a total loss. Probably a lot more than you think in the abstract.

yea broker suggested 250 but chubb wanted 750. seems like chubb wants to come on site.
honestly if 250 was really too low I would up it, but chubb may also be trying to make money by having customers over-insure. i'm in a near luxury high rise. i have near top end appliances. but i do have marble an granite finishes everywhere. the biggest risk seems to be from a broken pipe somewhere. and even in the case of fire the building has sprinklers. question is are you insuring for what event? if i ha a goo argument i'd consider 300-350.

Do you really want to have every content of your home restored exactly as is if a fire (and subsequent smoke and water damage) destroyed it all? Probably not. You would probably start over with less stuff and be happier for it. So don't insure for any more than needed.

Do be sure to buy enough ALE. ALE is the additional living expenses if you have to move to a hotel while your apt is repaired. In NYC this can really add up, esp in a disaster such as Sandy when many are displaced

Contents and additions/alterations are different buckets of coverage.

Chubb inspects to make sure that you are insured for the ENTIRE apartment, not just for the $$ amount that you have self selected as important to you (eg the kitchen).