Sounds far fetched to me to be honest, 10gil per sparkler = billions needed to make the sort of gil SE are talking about.
Also the ash needs to be farmed first.
Thought I did hand in a lot of ash the week before the suspension, well enough to get 200ish of each sparkler (as my wife loves fireworks in game, so I wanted enough to last her a year or so...), I could have got a lot more, but was bored silly after handing in that many as it was.
