We have to take the $750,000 USD if at the final date in January 2019 has the currency above 0.7340. That is a risk but we use USD to pay for many items so it will get used.
I just love spin doctors and financial engineering.
Without knowing a little more detail about the costs, dates and other specifics...
You have sold a USD put option with a slightly out of the money strike price (but I suspect you did not receive any premium for doing so) and as you have to take 3x the set amount, it is quite some premium. They have then used some of the premium you should have recieved to push the effective AUD/USD exchange rate higher. So the strike may have been 72.75 for example and the premium (3x .50 say) was part used (0.65 for you and .85 for them) to push the effective price to 73.40.
Now the twist, unlike you selling a straight forward put - where you receive the premium regardless of the outcome. Here you only receive it if at the exercise date the USD has weakened above 72.75 (plus the premium buffer the counterparty has allowed) of 0.65 so 73.40 (in my rough figuring). So - if it is between 72.75 and 73.40 the counterparty who set this up just closes the trade using part of the premium you would have recieved if you'd been given the transaction as a put option sale and pockets a .85 cent profit. If the USD does not weaken at all (in my figuring) they make 1.5cents (for no risk) and you get nothing for bearing all the 'risk'.
Regardless of whether you are happy or not to wear this risk (happy to lock in that exchange rate) - you are being spun. This stuff used to be tried on unsuspecting fund managers in the 80s and 90s (and new ones since then who haven't any knowledge of cashlfows and options). The names change (get repackaged by the spin doctors) but the outcome is the same - fee gouging at no risk for the seller.
There is a little more to it but not much. As the interest rate differentials now have the AUD strengthening against the USD - the AUD is priced in the forward market at a higher value - making it an easier sell.
With the recent plunge in the AUD - volatility has increased ... The put-call parity comes into play and voila - 'Binary options, knock-out options, leveraged forwards...'
Did you have to sign a derivatives risk understanding document by any chance or did they use the 'professional investor' exemption? Hopefuly you do not have to put up much of a margin (yet)?