You need to consider different kind of currency in your script: if someone is using Euros (€) it will not work.
I just replaced all occurrences of '$' with the variable CURRENCY and now the script works.

Example:
ORIGINAL:

function formatPrice2(text){
return parseFloat(text.substring(text.indexOf('$') + 1));
}

MODIFIED:

//var CURRENCY = '$' ;
var CURRENCY = '€' ;

[...]

function formatPrice2(text){
return parseFloat(text.substring(text.indexOf(CURRENCY) + 1));
}

I wrote an implementation that does this, but grabs the currency from AliExpress itself:

https://gist.github.com/Biotronic/7afca676b5f6c48ca1f26cb797fcda60

Feel free to use the above code, though there may be some rough edges.