Costs depend heavily on the country you are sending from, the weight, and the speed, so I will not quote figures that would only mislead. The general shape is consistent though: domestic letters cost very little, international postcards and letters remain affordable, and parcels are where costs climb quickly, with price scaling by weight and by how fast you want it there.
Economy or surface options can be a fraction of express prices if you are patient. Every national postal operator publishes a rate calculator on its official website, and that is the only source worth trusting since rates change regularly.
Tracking is now standard on mid-tier and express international services and usually a small add-on for basic mail; insurance is typically available up to a declared value for a modest fee. For anything genuinely important, whether documents, electronics, or gifts of real value, always pay for both tracking and insurance, and photograph the contents and the sealed package before handing it over. If the item is irreplaceable, consider an international courier instead, since their claims processes tend to be easier to navigate.