You have a problem with your code formatting and syntax at the very least:

function ref_access(){
global $error;

if (is_user_logged_in()) // <-- problem here...
$newdb = new wpdb( 'user', 'pass', 'db', 'localhost' );
global $newdb;
$hf_username = wp_get_current_user();
$inputValue = $_POST[$quanid];
$wpdb->insert( 
$table, 
array( 
    'ItemID' => $quanid
    'Price' => $inputValue
    'user' => $hf_username
), 
);

{ // <-- problem here...

}else {
     $error = "Error: You must be logged in to submit prices";
     return ; 
     }
}

Correctly formatted:

function ref_access(){

    global $error;

    if ( is_user_logged_in() ) {

        global $newdb;

        //you are not using $newdb anywhere in this functions
        $newdb = new wpdb( 'user', 'pass', 'db', 'localhost' );

        $hf_username = wp_get_current_user();
        $inputValue  = $_POST[$quanid];

        //you need to delcare global $wpdb here if you plan to use $wpdb instead of $newdb
        $wpdb->insert( 
            $table, //there is no $table variable within this function
            array( 
                'ItemID' => $quanid
                'Price'  => $inputValue
                'user'   => $hf_username
            )
        );

    } else {
         $error = "Error: You must be logged in to submit prices";
         return; 
    }

}

Update:

With regards to your comment about $table being defined in another function, you need to then pass the valuue $table to your function call ref_action('my_table_name').

Example:

function ref_access($table="") {
  //function code
}

//Usage

ref_access('my_table_name');