My mantra in buying most things is to always buy top quality products. Yes you might have to save up before getting them but generally you only need to buy once rather than replacing it after a few years. 
In the end you spend more money if you buy the cheaper alternative 
It mostly works like that, but not always.
E.g. A very cheap fluorescent fixture with crap tube and aluminum windings, which cost 4 times less than a proper one, but you will end up spending more than if you buy the proper one, because you will need to change it all the time.
Not the case with the arms, as Medved said, for the mass installation it is better to buy proper ones, because they will leave them with no maintenance forever. But we enthusiasts have the luxury of giving maintenance because we don't have much fixtures and all of them are likely to be in the same place, so suddenly a cheap arm from a scrap becomes cheaper.
Another option would be to buy a steel pipe of the same quality as the arm but for 10 bucks and get 3 arms from it, then you bend them and they will last as good or better than the commercial counterpart, for way cheaper, but then again that's something exclusive to us enthusiasts who "operate" at low qualities, for municipalities who install thousands or hundreds of thousands that becomes ridiculously expensive, so they'll stick to the commercial one.
The added value in arms is the bending, the treated steel pipe is cheap but of course the massive quantity buyer cannot bend the tubes by himself, so they'll charge an important amount for the bending process despite that process is super cheap. They might mold the steel in the bended shape from the beginning, but that "bended shape" charge is still there. Also a bended tube is inefficient to ship, so there's another important cost.
The problem here is he needs a bunch of them so the "cheap" $35 becomes a not so cheap $250 . $250 might as well be a million when you're his age.
That's another problem, and that's why he's looking for a cheaper alternative. For you 35 bucks might be nothing, but for that here you buy groceries for a week and for me that's a couple months savings because I'm still a teen, but then you multiply that 35 bucks and becomes impossible to afford.
