Sure why not. It's cheaper but not necessarily better to produce them yourself.
There is a massive over supply of weapons right now and it takes a lot of time to get your own corporations to the right quality level. Not to mention that when you don't need any more new weapons they are not at all profitable right now.
On the other hand having control over your own production is something a lot of players consider really important.
It's a trade of that you have to decide on for yourself sorry I can't help you with that choice.