Find the maximum difference between two fields in one query?

Question

Django

There is a model:

class Ground(models.Model):
    current_cost = models.DecimalField(_("Текущая стоимость"), max_digits=21, decimal_places=2, blank=True, null=True)
    cost_intermediate = models.DecimalField(_("Ожидаемая стоимость"), max_digits=21, decimal_places=2, blank=True,
                                            null=True)

How to get the maximum difference from these two fields?
It turned out to be done using aggregate, but it only returns the maximum difference, and not a queryset on this object