[_-__---]

So replenishing venom supplies may result in an increased metabolic load post-extraction, but that increase may not be so much when compared to another method of hunting. For example, it's probable that the heightened metabolic load associated with a python crushing/strangling its prey is a substantial increase from the animal's ~ergodic resting state.

If anyone has numbers on this, please link them!

Also, injections are probably not going to be clean and ideal. Having a toxin that does the job o(1000)-fold with a full delivery volume will still do the job with a tiny fraction of that in the event of a partial toxin delivery. This will still result in the death of the prey with a single, albeit flawed, attack.