Byzantium. The surprising life of a medieval empire – by Judith Herrin

In the economy chapter, apart from the often overlooked hard-ass (gold) and long-ass (700 years) of monetary stability, the author discusses some social aspects of economic life. The Byzantine elites, following on Ancient Rome’s disdain for commercial endeavors, typically opted to invest in three things: Land, administrative offices (which could confer some coin in unofficial ways), and titles in the Court.

A Byzantine celebration, as copilot imagined it. In the other versions, people were so hardcore eastern orthodox christians that even had halos.

The Court titles had fancy names and came with regular allowances. The more mundane ones had a rate of return of 2.5%- 3.0%, while the higher-ups (like Protospatharios, loosely meaning First Sword Bearer, with responsibilities that oscillated among Chief Bodyguard, Receptionist and Master of Ceremonies) reached 8.3%. Since Byzantines had also inherited Rome’s practise of capping interest rates, we know that a simple citizen could lend at a rate of 6.0% (a banker at 8.0% and a distinguised person like a Senator at 4.0%).

Re: Byzantine interest rates, from the impressive but rather dry, A History of Interest Rates – by Sidney Homer & Richard Sylla

So, it mostly did not make sense to buy a Court title, money-wise. Unless you did manage to land as the Protospatharios, so you could enter a risk-free carry trade of 2.3% and also enjoy lovely red robes with gold lining or white robes and a golden mantle (the latter attire was reserved for eunuchs). Half-joking aside, the titles were not transferable (that is, no secondary market), so you could not probably even get back the initial investment. It turns out, fancy names / clothes/ duties/ company were a major factor, after all. And secondary markets serve a purpose, at least sometimes.