Objection 1. It seems that there is no vice opposed to meanness. For great is opposed to little. Now, magnificence is not a vice, but a virtue. Therefore no vice is opposed to meanness.
Objection 2. Further, since meanness is a vice by deficiency, as stated above (Article 1), it seems that if any vice is opposed to meanness, it would merely consist in excessive spending. But those who spend much, where they ought to spend little, spend little where they ought to spend much, according to Ethic. iv, 2, and thus they have something of meanness. Therefore there is not a vice opposed to meanness.
Objection 3. Further, moral acts take their species from their end, as stated above (Article 1). Now those who spend excessively, do so in order to make a show of their wealth, as stated in Ethic. iv, 2. But this belongs to vainglory, which is opposed to magnanimity, as stated above (Question 131, Article 2). Therefore no vice is opposed to meanness.
On the contrary, stands the authority of the Philosopher who (Ethic. ii, 8; iv, 2) places magnificence as a mean between two opposite vices.
I answer that, Great is opposed to little. Also little and great are relative terms, as stated above (Article 1). Now just as expenditure may be little in comparison with the work, so may it be great in comparison with the work in that it exceeds the proportion which reason requires to exist between expenditure and work. Hence it is manifest that the vice of meanness, whereby a man intends to spend less than his work is worth, and thus fails to observe due proportion between his expenditure and his work, has a vice opposed to it, whereby a man exceeds this same proportion, by spending more than is proportionate to his work. This vice is called in Greek banausia, so called from the Greek baunos, because, like the fire in the furnace, it consumes everything. It is also called apyrokalia, i.e. lacking good fire, since like fire it consumes all, but not for a good purpose. Hence in Latin it may be called "consumptio" [waste].
Reply to Objection 1. Magnificence is so called from the great work done, but not from the expenditure being in excess of the work: for this belongs to the vice which is opposed to meanness.
Reply to Objection 2. To the one same vice there is opposed the virtue which observes the mean, and a contrary vice. Accordingly, then, the vice of waste is opposed to meanness in that it exceeds in expenditure the value of the work, by spending much where it behooved to spend little. But it is opposed to magnificence on the part of the great work, which the magnificent man intends principally, in so far as when it behooves to spend much, it spends little or nothing.
Reply to Objection 3. Wastefulness is opposed to meanness by the very species of its act, since it exceeds the rule of reason, whereas meanness falls short of it. Yet nothing hinders this from being directed to the end of another vice, such as vainglory or any other.
Source: Summa Theologica (New Advent)