I think you’ve totally missed quite a lot. You’ve also missed out on Wavelab 7 then? And you have to pay the full price?! And you’ve missed it by several MONTHS.
Even without the grace period it’s not going to be near Eur500 to upgrade from C5.
You could wait on spending your money with Steinberg for a year or so and hit the next grace period. You’ll lose out about ten Euros. If you’ve got C5 and happy with it then C6 won’t take you to heaven just yet although it has some handy features.
And if it’s a wind up you missed April fools day too.