Cold boot times are around 5m but if your usage periods are predictable it can work out ok. Works out at $2 an hour.
Still far more expensive than a ChatGPT sub.
https://modal.com/docs/examples/vllm_inference
or give this a go
https://modal.com/docs/examples/opencode_server
You get $30 free credits each month on Modal which is enough to play around (i have no affiliation, just think they run a great service)