If you want to be pedantic, your last paragraph does not have 6 sentances.
In this case, I will refer you to your previous paragraph:
Yes, there are budget ways to mitigate rust out. You can put a lump of some kind of compound or fiber over or inder it that may stick up lumpy. That way takes thickness to be viable. Fiberglass reinforced filler and epoxy filler are used over a welded repair all the time in an effort to prevent cracking or reaction to finishes.
Yes, it does take thickness to be effective. And in the case of someone wanting to fix a pinhole in a way that maintains its structural integrity and prevents it from spreading, who cares?
For a professional restoration, welding in a panel is the correct solution. For a daily driver, a floor that is not perfectly smooth on both sides is just fine.
The cost of the welder is only one of many considerations. Having a place to weld, getting replacement panels, the time/material cost investment to learn how to not make it worse all add up. Alternatively a $5 tube of jbweld and an afyernoon will make it just as safe.
You can make as many straw man arguments as you like about junk fixes that someone could attempt, but that does not change the *fact* that there are durable, safe, and sufficient solutions other than welding.
Had you said that welding is the *best* way, I would not have disagreed.
