There is no guarantee that the new part will be any better than the previous one which broke because it was run over. The old, welded part(s) will surely be much better because there will be more weld contact area and probably done on both sides, not just the outside (easiest to do with the hurry up wire feed that made it on a production line.
The fact remains that these links are contained by pins that are secured by flimsy rings like that used on sets of car keys. Weeds, branches and other stuff pull at them and finally pull them out. Then the mechanism goes snafu.
So. by learning to straighten and weld them, you are prepared to fix them again and again until you solve the problem that caused the pin dropout. Once you have a welder and can use it (I only have a Sears a/c buzzbox), life changes. I do cast iron, repair, new items and winter tool warming with this equipment. The next thing to do with his mower is to repair the blade gouges with weldment. Good as new. And balanced. Or as you say you can spend $100 for a set of blades each time you hit a stone or a piece of iron, or the pins you knocked out last time and could not find in the field. Maybe you should replace the mower spindle(s), too because the imbalanced blades will wear the bearings.