When a listing appears with no postage prices listed, firstly read the description of the item thoroughly, as some sellers tend to type it into the body of their description.
If you find no mention of postage prices at either the bottom of the page or in the items description, message the seller AS SOON AS POSSIBLE for a quote on the postage prices, DO NOT leave it until the last day of the items listing for contact, as a lot of sellers won't have the time to answer all messages within a day. Be sure to include your state/territory (and country if applicable) in the quote, for prices can vary quite a bit.
Be wary of sellers who will not respond to a message about postage prices, AND DO NOT BID ON THE ITEM THEY ARE SELLING, as they may be:
a) deliberately keeping the postage prices secret so they can make up any potential losses on an underperforming item they are selling, or
b) being sneaky by waiting till somebody bids for and wins the item, then overcharging on postage hoping that since you have won the item, you will have no choice but to pay whatever they decide for postage.
It is common for overseas sellers to not list postage prices for every country available, as it can be just about impossible to get a quote for every country, so please only ask them for a quote if you are genuinely interested in the item they are selling.