The 280 AI is an interesting round and it is also a nice looking round:-

That is the first fireformed case from the new chamber.

However to answer your question:-

[Quote] Is it worth putting $800-900 into a new barrel?

Unless there is something about the stock and action you really like then no i do not feel it is worth it. Sell the Weatherby and buy a donor to build the 280 AI on. I am sure you can pick up a suitable donor rifle at a reasonable price one that is probably better made and fit a premium barrel of your choice in the profile and length of your choice.

My own 280 AI started with an old BSA 1st Pattern Monarch in 270 Win that I picked up several years bacl before I found a Nice example of the 1st Patter Monarc. I paid Ł25 for the poor condition one it now has a new BSA barrel that I altered to fit the Monarch action.

It was in 7x64 but in the alteration I reamed it out to 280 AI the only drawback is that the BSA barrel is from the CF2 line and they were only 22" long and I would have preferred at least 24" but this was the only way I could afford to do this as a new barrel here in the UK from other sources would ahve cost quite a bit more than your $800-$900 in fact one gunsmith quoted me over Ł800 just to rechamber and fit this CF2 barrel!

The stock will have to be replaced as a previous owner sanded it severly and the fore stock is very thin but an unsure if to get one of this shape (Majestic Feather weight) or a Monarch stock:-

So I say go for it!