If you want to show all group price then you need to call group_price attribute resource model $attribute = $ProductObject->getResource()->getAttribute('group_price') of that particular product
and using afterLoad() ($attribute->getBackend()->afterLoad($ProductObject)) You will get group prices value in array of a particular product which include group price and respective customer group id
You can use
$groupPrices = $ProductObject->getData('group_price');
$Groupprice= $groupPrices;
if (is_null($groupPrices)) {
$attribute = $ProductObject->getResource()->getAttribute('group_price');
if ($attribute){
$attribute->getBackend()->afterLoad($ProductObject);
$groupPrices = $ProductObject->getData('group_price');
}
}
/* check group price exit nor not */
if (!is_null($groupPrices) || is_array($groupPrices)) {
foreach ($groupPrices as $groupPrice) {
if($groupPrice['cust_group']=='Member_Subscription_Id'):
// Customer id match & group price show
echo $Groupprice = $groupPrice['website_price'];
echo $GroupId=$groupPrice['cust_group'];
$formated_price = Mage::app()->getStore()->formatPrice($Groupprice);
$formated_price_incl_tax = Mage::app()->getStore()->formatPrice(
Mage::app()->getStore()->convertPrice(
Mage::helper('tax')->getPrice($ProductObject, $Groupprice, true)
)
);
endif;
}
}
Another Example: https://magento.stackexchange.com/a/36216/4564