Compared to what? 9mm Luger?
SFRC has 30 boxes of American Eagle ($0.74/rd) and 99 boxes of FN ($0.66/rd) in stock at this moment... and they can get more.
http://www.theammosource.com/index.php?main_page=index&cPath=1_108_765
There are several local stores here in Vancouver that have it in stock all the time as well, and others online. You guys are thinking of 8-10 years ago.
4.6x30mm (MP7 ammo), now that is "unicorn", but there are several guys around my neck of the words that source it for their MP7's. It's all how much you are willing to put into it.
If the most you are willing to put in, is to walk into any gun store anywhere and be guaranteed to buy a box, probably the Five Seven and PS90 are not for you.
They are exotic firearms. They are not practical utilitarian "truck guns", nor were they ever offered to the civi market as such. If you want to drink from the exotic waters of your TV/film/video game dreams... go for it. If you want a restricted firearm for anything beyond shooting at an approved range, you're in the wrong country. If you want a non-res PS90 for shooting gophers... you are a rich farmer being silly.
My wife and I learning to shoot a freind's PS90 6 years ago. Lightest recoiling centrefire firearm I have shot.