Cost of international swaps

I live in the United States. A few weeks ago, I sent a swap to Italy, and it was $3. Today, the postal workers would not take the swap in a regular envelope. It was $15 to send the swap as a "package", and I had to fill out a customs form.

What is the best way to send an international swap?

I send them in large or rarely in small envelopes. Without the tracking number, paying with stamps. I bought a bunch of stamps on eBay below the face value. You can determine the price following the following link.
​​​​https://pe.usps.com/text/dmm300/Notice123.htm#_c341

I don't declare anything, but the envelopes should be flat, so that they are processed automatically. So far, I didn't have any problems with international shipping. Everything was delivered, and rather quickly. The last one was delivered in 6 days to Germany a week ago.

It is not allowed to send cash by mail. If you tell that you are sending coins at the post office, they may deny it. And if the package is not an envelope (regular or large), they will charge as a package, which is much more expensive.

Sending from Israel seems to be a piece of cake compared to the USPS: nobody asks you what you are sending, no declaration necessary and the cost for up to 20 coins, trackable (registered) is about 5 $.

In Canada it costs about $12 Cad (~8u$) to send up to 200gr (~6oz) so long it is a flat envelope (which could be bubble). There's very little difference (less than 1$) to send an airmail letter or a small package. With a package you have to declare the contents and value though.
Registered costs considerably more, starting at about 25$ (~18u$)

It would be interesting to see when the postal services became so greedy! I'm old enough and remember when postal fees were sane!

Verweis : "Dejan"​Sending from Israel seems to be a piece of cake compared to the USPS: nobody asks you what you are sending, no declaration necessary and the cost for up to 20 coins, trackable (registered) is about 5 $.

​And here I thought everywhere else was the same way. That's crazy! It's at least $3 or more for registered within the US let alone international. The last time I sent coins out they tried so hard to get me to tell them what was in the envelope, making off hand remarks and seeing how I reacted to it I just kept saying "hobby items" and they final stopped prying and just sent it out.

Sending from USA to Europe, and specially to Italy, declaring that the envelop contains coins, can become very costly for the receiver if the custom fees are requested. Last time I hade to pay 18 Euro to be able to get the envelop.

I recently mailed right around 50 common coins to Italy from the US and it was between 24-25 USD. The standard is if the package contains things other than documents (paper) it is a parcel and must go at those rates. The cheapest parcel to Europe from the US is 14.50 USD from what I can tell. Now I have been able to slide 2-3 coins in an envelope and get them through. However, I have not tried to put many more in and just put stamps on it as some have suggested.