Turns out calculating the price of rose seeds being sold in South Korea in precisely the year 1940 is not as fun as it may seem.
Before late 1941, Korea used yen as currency. While not technically Japanese yen, it had the same value. Boom, 30 US dollars into yen. Now you have to convert for inflation. On yen inflation calculators, it only goes back until 1960-ish, so I had to dig through Wikipedia for the raw data and do the math by hand. All of this left me with four things to keep track of: The price of the seeds in USD in 2020, the price in USD in 1940, the price in JPY in 2020, and the price in JPY in 1940.
It was not a good time.