While the ammunition is expensive, you have to remember that to get a Remington with equivalent ballistics you would have to get the .300 RUM and you will pay as much for ammunitionin that chamberingas youwill for .300 WBY Mag ammunition.
Actually the only way to get the velocities advertised by weatherby for the 300weatherby,you must use the weatherby brand factory loads which are noticeably hotter than the 300weatherby loads from the other manufacturers.The weatherby brand factory loads are significantly more expensive than the loads for the 300 ultramag using the same bullets.
I have a Weatherby Vanguard in .300 Wby Magnum and am very happy with it.
The vanguard has a 24" barrel compared to the 26" barrel for the mark V.The velocities quoted by weatherby for the 300weatherby,are for a 26" barrel.Therefore,even with the weatherby brand factory loads,you won't likely achieve the weatherby quoted velocities without exceeding the design chamber pressure.
The simple fact is that most people choose the vanguard over the same rifle sold by howa in the non weatherby chamberings is because they think the weatherby name stamped on the receiver somehow makes it a better rifle.Or perhaps because they take the weatherby name to be some type of status symbol.