[lugerholsterrepair]

how come original magazines are so expensive?

The Luger magazine is fragile and expendable. They were not all that well made by their nature..NEVER use a wood bottom mag for shooting. You would be risking a wooden bottom cracking or the mainspring kinking up.
Plus the older the more rare. And they ain't making any more! Buy any you can get hold of..they will likely not go down in value.