Cost is always an issue, but I'd like to contribute just a few thoughts.
About 10 years ago I had a brief fling with a Lexus - (I still have it, still enjoy driving it, but like a husband the glamour has faded - but I still love it and depend on it.) Anyway I tried to negotiate the price down and the salesman responded with something I'll never forget...
If you aren't selling junk, you don't have to give it away.
Over the past ten years I've only spent money on normal maintenance items - the most persistent problem has been that it's burned out three right turn signal lights. About a month ago I had two problems, the back streetside electric lock wasn't operating properly and the rear window washer wasn't putting out water. Both were fixed for under $50. So I spent "too much" for the Lexus, but it's paid me back for ten years! Ask me about my former bargain car? Eeewueee... not so much.
When I got my Airstream 3 years ago, there were 3 other Airstream owners at my home RV Park. Last week there were 7 parked on site at one time!!!!!! I know for a fact that two of the members with older SOB's were influenced by seeing mine in person. If you think new Airstreams have quality issues, look at the new SOB's.... pure garbage!
You're buying axles for the next 20 years.
The cost spread over that time may be far LOWER if you get the best - simply because they'll last longer, protect your Airstream from vibration damage and cost you less in maintenance.
However ANY new axle properly sized and installed is probably better than towing on one that is shot.
Last thought. I wanted a quick, no appointment, no stress haircut so I decided to run into "The Hair Cuttery" which is famous for it's $12 haircuts. The local one is in a huge strip center with another salon just a few doors down. As I was walking to the front door, I noticed a sign in the window of the pricier place that said, "We fix $12 haircuts!"
It worked for me, and I got a great haircut for $20 - I ain't all that pretty to start with, so I sure don't need a gawdafful messed up haircut that will make the situation worse.
See you down the road, Paula
Today is a gift, that's why they call it the present.