Why ask here? Ask them

But I know these offers from the airlines on my former job: the discount is mostly ONLY on the basic price-on tip of that are various supplmts-like for his-season, porttax, fuelsurcharge + others.

Perhaps there is even another ferry that does not give discount but has at the end even a lower final price. These discounts are often just a marketing gimmick-and too many people think that then its better. Use brains and get smart

Most if not all of the “Offers” that give discounts for passholders are at the will of the companies involved and have no guarantee of them being available, as advertised or even good value.

It’s always best to compare to a booking without the discount as some can be so restrictive that the public rate including any regular offers is actually better value than the interrail discounted price.

That’s not to say that there aren’t any passholder benefits that offer real savings, many do, just don’t assume you are always being offered a bargain.