I found that email in my spam folder. Oddly, it did not originate at Waves, but came from a marketing company (mymarketing.co.il). That's how it ended up in my spam folder. Before taking it seriously, I verified that the return-reply address (Kswaves.net) is a registered domain of Waves. The marketing company is based in Isreal (where Waves is) so I was satisfied that the email was legit.
The subject line is misleading, though. They're not $15 each, it's a bundle of 10 plugins for $150. And none of them interest me.