Since this exercise was too simplistic I decided to do it in GolfScript

{\.'0'+\if}:bonus;

You can call it like this (with 0 being false and 1 being true):

1000 0 bonus
1000

1000 1 bonus
10000

Explanation:

• {} defines a block of code
• :bonus assigns this block to a variable named bonus
• ; pops the block off the stack since it's assigned to a variable anyway

The "function body":

• \ swaps the top 2 stack arguments, so e.g. 1000 1 becomes 1 1000
• . duplicates the top of the stack, so 1 1000 becomes 1 1000 1000
• '0' pushes '0' on the stack, so 1 1000 1000 becomes 1 1000 1000 '0'
• + concatenates the top two stack argument, automatically coercing to string if necessary. The stack is now 1 1000 10000
• \ swap the top 2 stack arguments again, so 1 10000 1000
• if pops 3 elements of the stack, if true (1) outputs the second (10000) otherwise the third (1000)
• No explicit output is needed since a GolfScript program automatically prints the remaining stack when it finishes

In a more traditional stack-based language like Forth one could define the word bonus simply as :

: bonus if 10 * . else . then  ;

1000 true bonus
10000 

Here's an F# version of the function without obvious args, and really without any multiplication;

let payDay = function | true -> sprintf "€%d0" | _ -> sprintf "€%d"

But it works...

let pay = payDay true 100
// pay = "€1000"

QBasic!

DECLARE FUNCTION CALC$ (salary!, bonus!)
CONST False = 0
CONST True = 1
CLS
PRINT CALC(32, True)
PRINT CALC(32, False)

FUNCTION CALC$(salary, bonus)
    CALC$ = "$" + LTRIM$(STR$(salary * (bonus * 9 + 1)))
END FUNCTION

Ruby:

def total_salary(base_salary, getting_bonus)
    "$#{getting_bonus ? (base_salary * 10).to_s : base_salary.to_s}"
end

In Go.

import "fmt"

func finalSalary(salary int, bonus bool) string {
    if bonus {
        return fmt.Sprintf("\u00A3 %d", salary*10)
    }
    return fmt.Sprintf("\u00A3 %d", salary)
}

Python:

def get_salary(salary, bonus):
    return f'${salary * 10**bonus}'

Clearly, F# doesn't pay well enough.

Untested PHP attempt:

function get_salary( $salary, $bonus )  {
    return '$' . ( $bonus ? $salary * 10 : $salary );
}

JS Quick and dirty :)

function salary(salary, bonus) {
    return `£${bonus? salary * 10 : salary}`;
}