Avg fare from LaG Airport to W 45th street, NY NY

No more than $50.

It should be about $45 depending on traffic (with all the airport construction, this could be an issue at any hour), but I recommend the NYC Airporter Shuttle if you aren't in a huge hurry. Might take up to an hour for your trip, but they run every 30 minutes, pick up outside every terminal of LaGuardia Airport, drop off at W. 42nd/Port Authority Bus Terminal, and its a flat rate of $28.

Buy a pass at the airport good for subway and buses in the city. We took a bus from LaGuardia Airport to the northern end of Manhattan (It's been too many years), walked a couple of blocks to the subway and took it to our hostel. Best value for the week.

$40 including tip should cover it.

Apologies to Amy L., but I advise against the Airporter. It used to be a very reliable service and a good value, but the last time I tried to use it, it was in a state of complete chaos. It took over two hours to make a trip that should have been 20 minutes, maximum. I thought it might have been a random occurrence, but online reviews suggest the service is frequently slow and haphazard. It is cheaper than a cab, but probably not worth the headache.

Its a flat rate from any NYC airport including LaGuardia - approx $50 to anywhere in Manhattan

should be a flat fee of about $45

$75

It's approximately $35-40 taxi fare depending on traffic

There is a set far to and from the airport.  It includes bridge tolls and I believe it is $54, the last time I took a cab; there may have been an increase.

Trips from the airport to city are priced fixed in yellow cabs  

I believe it is $35-40