[SalesForce] Convert double to String

The format method automatically does the commas and periods or visa versa (depending on whether your profile is in the US or elsewhere)

Assuming the $ sign applies to all cases in your org you can simply use

Decimal input = 2000;
String output = '$' + String.valueOf(input.format());

Note the String.valueOf(). This is required because the input variable is defined as a Decimal.

Edit: I noticed a bug with the Decimal.format() method where it will not show any numbers past the decimal point if there are only zeros there, ex. $100.00. To solve this I came up with this method.

private String getCents(Decimal x){
    String y = String.valueOf(x);
    String z = '.';
    if(y.contains(',')) z = ',';
    y = y.substring(0, y.indexOf(z));
    if(x - Decimal.valueOf(y) == 0)
        return String.valueOf(x.format()) + z + '00';
    else return String.valueOf(x.format());
}

Then to update the example above, it would be:

Decimal input = 2000;
String output = '$' + getCents(input);

If in All, you want a sumatory of all values you can use that

<apex:pageBlockSectionItem rendered="{!isBuildReport}" >
                <apex:outputLabel value="Record Limit" />
                <apex:selectList value="{!recordLimit}" size="1" multiselect="false" >
                    <apex:selectOption itemValue="10" itemLabel="10" />
                    <apex:selectOption itemValue="50" itemLabel="50" />
                    <apex:selectOption itemValue="100" itemLabel="100" />
                    <!-- <apex:selectOption itemValue="160" itemLabel="All" /> -->
                </apex:selectList>
            </apex:pageBlockSectionItem>