indirection requires pointer operand and expected expression errors

I keep getting errors similar to these:

pitstop.cpp:36:23: error: indirection requires pointer operand

        ('double' invalid)

         cost = UNLEADED * gallons;

                          ^ ~~~~~~~

pitstop.cpp:40:14: error: expected expression

                    cost = SUPER * gallons;                               ^

#include <iostream>
#include <iomanip>
using namespace std;

#define UNLEADED 3.45;
#define SUPER {UNLEADED + 0.10};
#define PREMIUM {SUPER + 0.10};

/* 
    Author: Zach Stow
    Date: 
    Homework 
    Objective:
*/

double cost, gallons;
string gasType, finish, stop;

int main()
{
    for(;;)

    {

        cout <<"Hi, welcome to Pitstop.\n"; 
        cout <<"Enter the type of gas you need:";
        cin >> gasType; 
        cout << endl;

        cout <<"Enter the amount of gallons you need:";
        cin >> gallons;
        cout << endl;

        if(gasType == "finish" || gasType == "stop")break;

        else if(gasType == "UNLEADED")
        {
            cost = UNLEADED * gallons;
        }
        else if(gasType == "SUPER")
        {
            cost = SUPER * gallons;
        }   
        else if(gasType == "PREMIUM")
        {
            cost = PREMIUM * gallons;
        }

    }   
    cout <<"You need to pay:$" << cost << endl;

    return(0);

}