You’re being screwed. My certification class through SSI was 500 total. If his on sale price is 450 that doesn’t sound right. Basically he is saying you arent experienced in the conditions local to you and hes trying to con you into an entire new cert class to teach you how to dive in current conditions. Example:
I was certified at Vortex springs florida. I live in Chattanooga, Tn. and Wanted to dive the local river which is murky and has a visibility of 6.......Inches. The local dive shop told me I needed to take a river diving course and a boat diving course to know how to properly handle the conditions. I knew this was a scam so I went with an EXPERIENCED friend and have now logged more than 20 dives in that river. The best way to become a better diver is by diving.