Obviously, swords vary in quality. Ideally, I would like to know what a standard army issue sword would have cost, if I bought it privately. But I realised we may only be able to assert what this sword cost the army. Failing that, I would be interested in any recorded sword prices.
I have access to PART of „The Economic History of Byzantium: From the Seventh through the Fifteenth Century“. Therein I found no answer.
Another paper that will help to put your answers into perspective is this one. by B. Milanovic. It asserts that:
The average “modest” salary (including benefits in kind) for an unskilled worker was estimated by Morrisson and Cheynet (2002, p. 869) at about 1 nomisma (N) per month or between 10 and 12 N per year.