Factory chains are hardened, only the cross links not the side stringer, to reduce wear, if your only using them in dirt/mud should be OK but would not last long on paved surfaces, even the hardened ones wear pretty quickly. You could use those repair links instead of welding, that would speed things up.
They do make a huge difference, I mostly use chains in snow but was recently using my 2 WD tractor in the woods with new v-bar chains 4 link spaced, the ground was very greasy after some flooding rains, I was surprised how good it went pulling logs and pushing tree tops through the mud, I'm sure it would have gotten stuck just driving in there with out chains.
I know about the shock of the cost of chains at the dealer, mine wanted close to $500. for a set of rears.
I got a killer deal on chains I found through Graigslist close to my town, guy owned an auto parts warehouse and had several pallets of surplus chains, I walked out with 5 pails of chains for $150. had to mod some but others were perfect fits. Made 3 sets of large rears, and 4 sets of fronts and garden tractor rears.
I looked and looked, asked everyone for used chains, couldn't find anything but got lucky with this find, there's still pallets of chains there but it's in CT.
Good Luck, JB.