Fwiw my web app costs like $80/mo in hosting fees, and could be done for even less. I forget how much we paid to register our company but it wasn't much. The startup costs aren't that much, it's mostly time.
I wouldn't be so optimistic on a few months to start generating cash tho unless it's a simple yet novel idea.
I could spare that much, but the idea in question is a bit different. Without going into too much detail, each upload consumes some compute, equivalent of like 10 seconds on a M1 MBP with 16GB RAM when nothing else is heavy is running. So I think my costs will be a bit higher and I would need to start billing customers early on.
I wouldn't be so optimistic on a few months to start generating cash tho unless it's a simple yet novel idea.