WP User Query with meta queries

Actually, I think your code says

Where min_price >= $price and max_price <= $price.

Try to switch the operands, like here:

    array(
        'key' => 'min_price',
        'value' => $price,
        'compare' => '<=',
        'type' => 'NUMERIC'
    ),
    array(
        'key' => 'max_price',
        'value' => $price,
        'compare' => '>=',
        'type' => 'NUMERIC'
    ),

It works for 10.000 and 20.000 since you use the bigger/equal and lower/equal operator.