Mission Frustration

I'm relatively new here, so I went down the track of one mission. Finish mission 29. I start mission 30... its literally not for sale. Its a dukka coin. 750. The highest amount available is 250... in theory I could buy a 250 coin for 7mil, then one for 8mil, then one for 9mil...
I obviously do not have 24 million MP. If I could buy 750 1 dukka coins for the lowest price available(clearly the price would go up per coin) it would cost me 14 million MP. I do not have 14 million MP.
In essence this is my fault because it says "you cannot go back once you start" and you cannot know the item until you start... but to be tasked with getting something that is on its face impossible(unavailable) and even using the work arounds(of course) would be 3x the money I have(at the cheapest)... after sinking the better part of a month, and at least as much money into the missions as I even currently have left over in the bank... is debilitatingly frustrating.
Its kind of crushing. Just an hour and 22 minutes until all my work will be useless. -sigh-
This is written to try to dissipate some of my despair. Life goes on.

Edit: Like I said, I am new to this. I have AU points, and they sell dukka coins there. So that's far less distressing. Neat.