Ironically, it might be getting easier.
ABC bullets in Salmon Arm makes a nice solid bullet.
Primers are coming in from overseas. Talk to ABC and ATR on that. I am sure there are other dealers but I am not up on the BMG supply.
Cases are still reasonably available but you will have some prep work to do as it is mostly mil surp. This will be the weak spot in the not too distant future.
Powder is a no brainer.
Presses and dies are now more common then they have ever been.
Cost - well if you have to ask....
If you are going to spend this type of coin and want accuracy, the custom route is better. Obtunded is working on bringing in 50cal match barrels. Ian Robertson and ATR can offer decent actions. Of course, Ian can also offer you a stock or two or 1000.
Triggers can be had from various dealers including myself. Bases, rings and optics are plentiful as long as you watch the contour of the action.
So if you have the dough, this is a great time to be looking at a boomer.
But understand, in general, a smaller cal will offer much better LR accuracy. The big cased 338's will keep up without any problem. Even the 6.5's and 7mm can reach out way beyond most peoples dreams.
Out to 1000yds, 6mm to 338cal will simply outshoot competition BMG's in mechanical accuracy on average. Of late, the 1000yd BR heavy class are getting turned on their ear by the 6mm, 6.5's and 7mm's.
Of course, all this small stuff will never hit as hard as the BMG but there is no discussion that a 300gr 338 MK has arrived either. This cal will get extremely interesting if Berger ever releases VLD bullets. Lapua is doing well but supply is not always great.
Enjoy your new toy....
Jerry