Sacrificing Trinisphere to Cabal Therapy

If you have a Trinisphere out and make it a 5/5 with Tezzeret, Agent of Bolas, if you sacrifice Trinisphere to flashback Cabal Therapy do you also pay 3 mana? Since Trinisphere asks last, it would not be in play after you pay the first cost (sacrifice a creature). Would it be able to ask from beyond the grave so to speak?

https://yawgatog.com/resources/magic-rules/#R601

Total cost is locked in at step F, costs are paid in step H. The Cabal Therapy costs 3 mana regardless of what you use to pay the alternate cost of sacrificing a creature.