That mudblood girl is also the most talented witch of her generation. Maybe Harrymort just wants another Bellatrix and this is the first step towards it. Maybe the debt doesn’t matter because Britain is going to be at war / Lucius will be dead before Harry would graduate. Also, Harry just gained a sworn minion out of it, which is arguably a lot more useful than a large sum of money.
That mudblood girl is also the most talented witch of her generation. Maybe Harrymort just wants another Bellatrix and this is the first step towards it. Maybe the debt doesn’t matter because Britain is going to be at war / Lucius will be dead before Harry would graduate. Also, Harry just gained a sworn minion out of it, which is arguably a lot more useful than a large sum of money.