Correct, GPT-4 is 20-30x the cost compared to GPT-3.5-turbo, but that's more in another class entirely. IMO a finetuned-GPT-3.5-turbo won't beat base GPT-4 for the use cases where you really really need GPT-4, but that remains to be seen.
The real alternative to a finetuned GPT-3.5-turbo is still the base model with a very very complicated system prompt.
The real alternative to a finetuned GPT-3.5-turbo is still the base model with a very very complicated system prompt.