I`ve said before similar to my previous posting before bye bye Maxjet and co. Silverjet could have pulled in "easy" cash in the better times with a 2 class product, whether the business and economy product or a premium economy and economy product.
That would have been a total mistake and was why MAXjet failed - it became a confused brand with a confused strategy that was not pitched correctly to those who could provide the best profit. Further, SJ's operation is focused on the business class product, and their terminal cannot accomodate economy passengers.
I am sure that, even if they do not survive in their current form, the SJ brand and concept will somehow survive. It is extremely focussed on its core market and provides a great product.
If any survive, they should.
(PS - £499 is a lot, when you can pop down the road to fly AA or BA for £300)