We would love to have this feature, and I have reached out to GMG multiple times in the past. Since we already have the 'special discount' setting, accommodating GMG XP prices should be a relatively straightforward task.
Unfortunately, we currently have no way of downloading these 'XP' prices, as they are not included in the GMG product feed. Despite our efforts, we have been unable to persuade the store to add these prices to the feed or provide the pricing information through another method.