The 338 Edge is a custom "wildcat" cartridge BUT, factory ammo is offered by Applied Ballistics. You get a choice of 300grn Berger or 250grn Berger:
You have a point about the short bbl life of the 300RUM, fact of life: If you want to play, you will have to pay. The 338's will offer substantially longer bbl life; how many 338 cartridges can one purchase at the cost of a new 300RUM bbl?
I would expect a legit bbl life of 1k rnds from the RUM if you mind your manners, keep it clean & don't shoot it hot. One of our senior members (Broz) has well over 1k rnds through his 338 Lapua & it is still going strong.