@Riger Several things here:
1) She managed to have more debt than her entire country because the prices were so high for a single revival and you don't make it to a level so insanely high that you can do that without being competent enough to kill high level monsters. Even if she hit a skill/level wall where she couldn't take on the appropriate monsters ,she could have farmed lesser monsters instead, (eg that other dude one shotted platinum slimes despite them probably being melee resistant) unless the fees were so exorbitant that it was impossible to make any headway. We haven't heard anything about interest rates so this is just obscene price scaling alone that I'm assuming is doing that to her and other heroes.
2) This continues on point one. It should be physically impossible to rake in an entire country's GDP per death. Given the overall high quality of the clothing and the staves, we can assume post renaissance and lack of guns means we can say this is pre industrial revolution. The fact that they have enough recordkeeping to make a GDP also favors the late medieval period at the absolute earliest and can easily mean we're right before an industrial revolution analogue kicks off. I'll pick France 1870 since this is probably a european setting and it's the one the japanese tend to think of the most. $72,100,000,000 is the GDP that Aegis reached. At a million bucks a death she would have had to have managed to die over 72 THOUSAND times within the span of a few years(gonna give her ten years to assume she started young since she's probably not a cake or even past 18) to possibly make things that bad.
In order to attain that debt she would have had to have died approximately 19,753,424.65753425 times per day with a small average fee of a million per death over the course of ten years.
I doubt there is enough physical gold on that planet to even try to pay. She didn't even start at a million bucks a pop. Why the hell did nobody even stop her and get her to retire before that point unless the point was to enslave her? I don't even think her current revival cost if she paid for one is physically possible as a real number value for money owned by an individual within her country.
3) It appears there are barely more than 3 heroes if his work load almost completely dissipated after torturing one hero and scaring another.
4) Where the hell is his share of this cash if a high level hero ranks in THAT much dosh per death? They never pay him enough for a damn janitor.
5) Her actually being capable of paying a single fee would collapse continental economies. This church is either a bigger threat than the demon lord, working with the demon lord, or secretly on the same side as the demon lord.
The more likely explanation to all of my ranting is that like most people, the mangaka doesn't realize just how much of an obscenity the difference between a million and a billion is.