It's a 20% discount on input and a 33% discount on output through at least November 21, 2026; the revised pricing schedule is now

    Model       Input  Cached input  Cache writes  Output
    gpt-5.6-sol $4.00  $0.40         $5.00         $20.00
    gpt-5.6-terra
                $2.00  $0.20         $2.50         $12.00
    gpt-5.6-luna
                $0.20  $0.02         $0.25         $1.20

So Sol is still 20x Luna, but much more appealing when compared to offerings from Anthropic and others.