Dear Peter Kong,
Maybe you upgraded the version of virtuemart component before, the prices are changed on your site now.
You can fix this issue by updating some modules such as mod_sj_virtuemart, mod_sj_vm_extraslider, mod_sj_vm_megaproducts, mod_sj_vm_slickslider.
Example: mod_sj_vm_extraslider => go to "modules/mod_sj_vm_extraslider/core/vmextrasliderreader.php", finding:
price.virtuemart_product_price_id,
change to:
price.virtuemart_product_price_id,
price.product_price,
-----
$product->prices = $calculator->getProductPrices($product->id);
change to:
$product->prices = $calculator->getProductPrices($product);
Thanks
