...Their support largely consists of other users in support forums, with the majority of the cost absorbed by the client organisation.
In most cases I'd agree with you: vendor support is a dumbed down user forum much inferior to Stackoverflow.
However, it has been a couple of years since I last managed larger teams using this software, but the support from SAS was simply outstanding. Nothing like it anywhere else. You call, they answer and you speak immediately to someone really knowledgeable in the tool, in stats (the main use case for SAS), and, more often than not, in your industry. Never had to do more than one transfer to get anything resolved.
You pay for support but this is the only vendor where I ever felt you got your money's worth.
These days even the client realises that it is more data science and knowledge discovery, and less about stats which more or less zeros the value of the SAS support. I wish them well; by all accounts they were a great company to work for back in the day when they still mattered.