I have CSL and bought them in the original issue i.e. direct from the Seahawks before games were being played in the new digs.
The asking prices on that site are kind of ridiculous. The original cost for the center section (109, 135) were $3000 per seat. It was reduced somewhat if you were a many year season ticket holder and/or were willing to pay the entire fee all at once. Might have had some other discounts too.
BTW, the CSL is only for 30 years, and we're 10 years into that period, so if anything, you'd think they'd be worth less now, not more, but it is true that Charter seats tend to go for just a few more dollars per ticket than the better 300 level tickets, and obviously they are superior seats, though you are usually not covered by the roof.
It has turned out to be a good deal, given that the team has been careful to keep Charter tickets reasonably priced.