Write a function `variadic_sum(*args)` that accepts any number of numeric arguments (integers or floats) and returns their sum. If no arguments are given, the function should return `0`. For example, `variadic_sum(1, 2, 3)` returns `6`. You do not need to handle non-numeric types.
Constraints
The number of arguments is between 0 and 1000. Each argument is an integer or float. The sum is guaranteed to fit within Python's float or int range.