Pardon the essay, but
In this chapter and the last, many commented on the duke's gross spending.
However, remember this is a Korean webtoon for a Korean audience. The use of "millions" (in gold) is probably a reflection of Korean won, which is different to the dollar system:
1000 won = less than $1 USD
100,000 won = less than $100 USD
1,000,000 won = less than $1000 USD
So, "25 million" is appropriately adjusted to about 20 thousand dollars, and "100 million" to about 80 thousand or so.
Not nearly as stupendous-sounding as "100 million"... Nevertheless, it's an exorbitant amount to bid on pawned jewellery, for sure.
I am aware this is a fantasy with the currency being "gold" and it may not be equivalent to k-won, but it's still more plausible than it being equivalent to USD.
This bidding scene makes me a lil uncomfortable, too. But it's an indulgent fantasy romance, so whatever I guess.