I'm from Portugal and I'm here to explain the big question about these coins.
I'm a numismatist who knows a lot about this stuff.
I'll break it down into questions and answers to make it easier to understand.
Are they real?
The coins are real and can be used like normal coins. They're made by the Mint as commemorative coins. This explains the ‘strange’ denominations. There is a big difference here, as there is the cupronickel/silver 500 version (depending on the coin), which are the normal ones - sold by the Mint at face value; then there is the silver proof (non-circulating) version; and there are also some gold ones.
This shows that there is a difference between circulating and non-circulating coins.
Now comes another question - Do people know about their existence?
The vast majority do not. Apart from the numismatic community, most people are unaware of their existence. This leads to another problem: even though they can be used legally in shops, many people may not believe in their authenticity (due to lack of knowledge and ignorance on the subject), and you end up having to explain this whole story to them to make them understand.
Finally, how much do they cost?
As I said, at the Mint, coins (except for proof coins) are sold at face value. Numismatic shops usually sell them at a higher price. For example:
1.5 euro coins are sold for 3 or 4 euros; 2.5 euro coins for 5; 7.5 euro coins for 10; 8 euro coins for 12 and 10 euro coins for 15.
These values are estimates, as they vary from shop to shop. They are often sold by private collectors at face value plus 2 euros.
Summing up: Apart from the proof coins, they are worth their face value, being commemorative and legally usable in establishments. Due to a lack of knowledge, many people are unaware of their existence (also partly because they are only obtained from the mint), so it is necessary to make these coins known to the public.
Interesting fact: One of the last coins to be released was a €5 coin, commemorating a very well-known rock band (Xutos & Pontapés), which appeared in the news and on social media, introducing many people to the world of numismatics. This also led to a rush to acquire them, with private individuals selling them for more than €35 (the cupronickel coin; the silver proof coin already exceeds €150).
I hope this helps to clarify the issue.
Happy New Year!
DINIZ BRITES
Colecionador de notas e moedas antigas.