the real answer is what do you think 2-3 days of your time plus expenses is worth (plus additional time for any post processing work,)
How the images will be used usually has some impact on cost as well.
Personally for me I would add $1500(allowing for 3 days including post work) plus the cost of all expenses (flight hotel, per diem for meals)
that gives a base that pays for your time (which has to also cover equipment costs)
I'm probably also pretty low on the price as It's not my primary job, just an add on (but remember it removes you from your primary work so you have to cover that loss plus take into account your fixed costs like equipment)
Depending on the Tog it could be a hell of a lot higher - I think the fashion guys daily rate can be hellishly high
$10000 +++ if they are top names like Ben on here
So the real answer is what do you think your time is worth, start a little higher because it will give you room to come down a bit if need be.