Oh, right, I wonder what the next
few pages are about...
Oh yeah, it is about how not a single person in the group has any idea what compound interest is, and the dude intentionally hid it the whole time. Can you actually read the manga before glazing it?
They knew about the interest the whole time, and had dutifully paid him back when they got the chance. This only became a problem when they took him for granted and decided to abuse the loan system. These are actual bums putting everything on the credit card.
They know about 10% per day, but they don't know it is compound interest. Why is this so hard for you to understand? It is literally in the manga; that is the goddamn premise of this story.
Even if we pretend, for the sake or argument, that he intentionally hid the compound interest in a cynical move to cripple the Hero's Party, they knew he would lend out points. They'd had these loans out for literal YEARS at this point without so much as remembering they have to repay him. If this kind of credit history could be pulled up at a bank... they'd be arrested on the spot for fraud.
No, they
calculated beforehand that they would still have enough skill points if he tried to ask for the loan back. The only thing they don't consider is that the guy is a loan shark who hides how his debt works.
That is to say, that if you want to repay a 1000 SP loan (What they owed at the start) in 10 days, you'd need to get 110 SP a day. If you decide to pay it back in 70 days, the loan doubles, but you had 7 times longer to repay it, leaving you with a daily payment 3.5x lower than when you started. At 120 days, your daily repayment amount stop decreasing the longer you wait (I.e., it's becoming less efficient over time to not pay it back, so you need to work harder than before from now on), and at 380 days you're paying more, on average, per day than if you'd just paid off the loan in the first 10 days.
Your logic is so comically bad that it genuinely baffles me. When paying off compound debt, the sooner, the better. Do you know why it has a lower daily payment? Because you think people who pay off their debt are frozen in time while the guys still in debt are working. In reality, the other guy would still be working and earning every single dollar he gets without worrying about the loan.
Assume two guys borrow 1000SP; one pays it off after ten days, while the others hold on until 70 days. Both earn 110SP every day. After ten days, the first guy pays back his borrowed money and his debt(1000+100). And then every single SP he earns belongs to him. The other guy waits til the 70 mark to pay it off. Now, how many SP points each of them have?
First guy: 60*110=6600
The second guy, 70*110=7700, pays back his debt, which is about 2k=>5k7
Isn't it weird that the first guy actually turns out to be better? See, this is basic math. You are so busy defending a loan shark that you think late payment(til that magical 6-month mark) in compound interest is efficient just because the daily payment is lower. No shit, Sherlock, it is always the faster, the better unless you believe the money you keep can earn more money for you. But that is obviously not what you have in mind with that calculation.
Also, do you know why the party is fine with not returning it? Because they think it is a simple interest, not a compound one. Simple interest payments are the exact same no matter how much time passes. As long as they earn more SP daily than 100, they never risk bankruptcy. Yes, it is obviously still better that they pay off the debt, but it will never reach the point where they are at risk of running out of SP. Or at least that is how it should be if our glorified loan shark MC doesn't hide how his debt works.
Also, with your logic(which is horrendous, but I will give an example here to show you that your logic shot itself in the leg), the party's member have every reason not to pay back their debt when they think it is simply interest.
70 day=1700SP of debt=>24 daily payment
6 month=2800 SP of debt=>15.6 daily payment.
6 years=220000 SP of debt=>10.5 daily payment.
Do you see how, with your backward logic, the party actually pays less per day the longer they hold on to their debt, the debt which they believe to be the simple interest?
Yeah, the big difference is he's loaning to the Jeff Bezos of this world. They're literally a monster-slaying party. Their whole thing is to use the skills to acquire more SP. This isn't money, where you might be borrowing some for a sick mom or something, then also burning through it to just survive. The points exist solely to acquire more skills, and have no other use. So setting some aside after literal months to pay back the guy who did your learning for you is both a sound idea, and easy as fuck given your job. Look at it this way: They're investing the points into skills, making bank, and then refusing to pay the shareholder.
Ah yes, they refused to pay him back. Hmmm, I wonder what is this
here...
Oh, right, they return his SP to him because that skill can't take back the loan unless he gets an agreement from the party. The reason why they don't simply pay back the debt despite the fact that they obviously can and later do is that this is the usual brain-dead "The hidden OP MC was kick out of that party because his party's member are full of dumbass who don't realize his actual potential and contribution" manga; no one in these type of manga is allowed to have a little functional brain besides MC and his harem(their brain doesn't work that well either but at least better than none).
And you still cope with the fact that the guy literally hides how his debt works and his skill is a literal loan shark reference.