Loading 7 X 57 is no more difficult than .308, you just have a much larger selection of bullets in .308.
Once you have a supply of cartridge cases you are set for quite a while as with neck sizing and backing away from max loads you can easily get 10 reloading from each case.
I don't know that I ever bought reloadable 7 x 57 ammunition. If I did, it wasn't much of it.
I probably just got some to make sure the gun actually functioned.
As for neck sizing and backing away from max loads, I really can't do that. Gun is a semiauto.
I did pick up a few 7 mm bullets, but those were intended for a 7 mm Magnum. Maybe they are also suitable for 7 mm Mauser.
- Ivan.