I'm not sure how "one inhabitant" would be defined by a Tribunal - I'd think it's contextual, but in this case I'd go with "anyone annually supported by the Covenant".
"One Mythic Pound" is defined as "equivalent to a pound of silver, the annual income of a typical peasant" (Covenants, p 56). Since "typical peasants" did not have a lot of (read "not any") "savings", and since grogs and servants are not only fed, sheltered and clothed, but also paid a bit in addition, and since upkeep of Specialists and Magi (and their labs!) would typically cost quite a bit more than that 1 pd/year, 2 pds/inhabitant/year would mean that a covenant could cover its expenditures and have something (significantly?) less than 1 pd/inhabitant as "disposable income" for the next 4 seasons.
Now, the Tribunals don't care about "game balance" but about the inflation of local economies, so if a covenant claims 500 nightsoil collectors as "covenant inhabitants" (or is simply spending a smaller amount in an economically isolated area), they may find themselves in trouble, any wording not withstanding. They might (maybe) get away with it once, or not, but never more than that.
Likewise as far as game balance goes - SG's should shut them down if they feel things are getting out of hand, regardless of "the Law". And also likewise if magi try to cut corners and spread around large quantities of "Duration:Moon" silver instead of permanent species created with vis (or at least if they aren't smart when they do it!).
But meanwhile, if an average covenant is, say, 100 souls or less, a creative SG* can easily find excuses to immediately reduce the majority of the remaining 100 pds** and then find more reasonably attractive base expenditures (labs, basic comfort items, etc.), leaving them with only a couple/few dozen pounds to spend in adventures and improvement - which is not unreasonable, especially considering the expenditure of vis (and someone learning/inventing that spell!).
(* or one with the Covenants book, highly recommended if you care about expenses, not to mention labs, texts, building neighboring covenants or filling out the covenant's non-mage population.)
(** If Players think their Magi (and their Specialists) are living like "the average peasant" at 1 pd/yr, then constantly remind them with any unpleasant details of "peasant life" that you might think of. If they think they have more than one change of worn-out and coarse clothes, boots, warm cloaks, chairs (vs benches or stools), anything but the simplest and most repetitive food, wine, lamps (vs a few candles), comfortable beds, rugs or tapestries, jewelry, etc etc - they are not living "like an average peasant". No visitor will be impressed (nor stay long), no innkeeper or fishmonger will give them respect when they travel, no noble or priest will receive such shabby "wise ones" without cause! And that's before The Gift kicks in!...)
Of the 12 "stereotyped" magi of the 12 Houses depicted on the cover of the core book, only a few are dressed anything "like peasants" - and some of the rest are spending far more than their 2 pd/year share. On new, clean clothes, if nothing else!)