I guess I will be the first of the smiths on this board to offer my opinion on the Wby MkV.
There is a reason they are not used widely by top smiths, frankly, their design does not lend to consistant extreme accuracy compared to the likes of the Rem 700, M70 and even Savage receiver.
There is only so much you can do with a Wby MkV as far as accurizing the receiver and at times even fully accurized rifles on these receivers do not perform as they should.
Cost is not prohibitive if they were able to produce extreme accuracy rifles. Hell, look at the cost of the BAT and NEsika receivers, makes a Wby look relatively cheap but in those cases its money well spent. In my opinion, there are several other receivers that rank far ahead of the Wby for custom building.
There is a reason the Rem 700 is the most widely used factory action for custom rifles
. The reason is accuracy and strength. There is also a reason why the Wby is not as popular, it just simply is not as consistant.
Not to say an accurate rifle can not be built on a Wby receiver, hardly the case, just much more likely to get your moneys worth with a Rem 700 instread!!
Just one smiths opinion, I am sure others will differ.