This is really annoying problem and can be confusing for customers.
When you select a custom option on a product you can see +£3000 or -£3000 on the product display page. works up to Magento 1.4 -1.9.2.4 not tested on 2.0 +
Before:
After:
The Solution
Navigate to JS/Varien/configurable.js
goto line 249 and comment out like below using // shown in red
formatPrice: function(price, showSign){
var str = '';
price = parseFloat(price);
if(showSign){
if(price<0){
//str+= '-';
price = -price;
}
else{
//str+= '+';
}
}
var roundedPrice = (Math.round(price*100)/100).toString();
if (this.prices && this.prices[roundedPrice]) {
//str+= this.prices[roundedPrice];
}
else {
//str+= this.priceTemplate.evaluate({price:price.toFixed(2)});
}
return str;
},