... I see where Wally World has the Weatherby Vanguard chambered in .300 Weatherby Mag for $388.
I see where they are made by Howa in Japan but they claim to support the same quality criteria as those made in USA.

Any thoughts before I buy one?

You might want to research show much it cost to feed one of those things. I guess if you reload it's not so much of an issue.

It is a really good cartridge, about on par with the 300 RUM and a little faster than the 300 Win Mag.  Shells are pretty expensive though.

I do not have any experience with the Japanese made Weatherbys, but I have never heard anything horrible about Howas.  That is a decent price, but you can probably get a Model 70 or Model 700 - both excellent rifles with many more aftermarket options available - in 300 Win Mag for cheaper.