The old Savage Frontier Sourcebook (usual place) gives some example times for travel in the Sea of Swords but no costs - these are in the PHB. Luskan to Waterdeep with the wind would be, for instance, 2 days by a longship and cost (according to the PHB, Table 7-8) 1sp per mile. Do the measurement and multiply it up and the ball park figure will be 55gp though it could be a bit more obviously.
My players made a trip from Luskan to Waterdeep and it cost them exactly 10 days. That is also the travel time that is detailed in the second edition boxed set called "the North". So 2 days would be too fast. Depending on the weather/avalanches/pirates etc..., you can add or distract 1d6 days.
My players paid 200 gold pieces for their travel because it was the last ship that departed luskan before they closed the harbour for the comming winter.
The 2nd edition Moonsea accessory had a map with costs associated to booking passage between the various Moonsea cities.
Session Reports posted at RPG Geek. Stem the Tide Takes place in Mistledale. Dark Curtains - Takes place in the Savage North, starting in Nesmé. I wrapped my campaign into the Hoard of the Dragon Queen, but it takes place in 1372 DR.