After thinking about it, Lex couldn't exactly claim that the cost for hiding the Midnight Realm was expensive - and yes, there really was a price he had to pay. It seems the difference between something the system did itself, and something he did, was who paid for it.
Objectively speaking, the worth of the Midnight Realm was inestimable. No amount of MP he earned could cover even a fraction of the true worth of the Midnight realm, and keeping it safe and secure was one of his top priorities.
Seen from that lens, the cost of keeping the Void Aegis running at a measly 1 MT a day was not so bad. Except, that he couldn't afford that! Not ordinarily of course.
Technically speaking, the primary source of income for the Inn was renting rooms. It was an Inn after all. The secondary source of income should have been food, although he still wasn't satisfied with the quality of food that the Inn provided. It was pretty good, it was just that he knew it could be better.
