TIMTOWTDI...

use warnings;
use strict;

our $MIN = 1;
our $PFACT = 10;
sub price {
    my $weight = shift;
    return abs $weight < $MIN
        ? ( $weight < 0 ? -$PFACT : $PFACT ) : $PFACT * $weight;
}

use Test::More;
is price($$_[0]), $$_[1] for 
    [ 5.0, 50],[ 2.3, 23],[ 1.1, 11],[ 1, 10],[ 0.3, 10],[0,10],
    [-5.0,-50],[-2.3,-23],[-1.1,-11],[-1,-10],[-0.3,-10];
{    local $MIN = 3;
    is price($$_[0]), $$_[1] for 
        [ 5.0, 50],[ 2.3, 10],[ 1.1, 10],[ 1, 10],[ 0.3, 10],[0,10],
        [-5.0,-50],[-2.3,-10],[-1.1,-10],[-1,-10],[-0.3,-10];  }
{    local $PFACT = 5;
    is price($$_[0]), $$_[1] for 
        [ 5.0, 25],[ 2.3, 11.5],[ 1.1, 5.5],[ 1, 5],[ 0.3, 5],[0,5],
        [-5.0,-25],[-2.3,-11.5],[-1.1,-5.5],[-1,-5],[-0.3,-5];  }
{    local ($MIN,$PFACT) = (3,5);
    is price($$_[0]), $$_[1] for 
        [ 5.0, 25],[ 2.3, 5],[ 1.1, 5],[ 1, 5],[ 0.3, 5],[0,5],
        [-5.0,-25],[-2.3,-5],[-1.1,-5],[-1,-5],[-0.3,-5];  }
done_testing;

[download]

Update: Expanded test cases. Please check if this is what you want, keeping in mind the caveat that jo37 mentioned!

In reply to Re: Some simple math and absolute values (updated) by haukex
in thread Some simple math and absolute values by sidmuchrock

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