While there are undoubtedly more flaws, I'll point out the 2 most prominent ones in your post.
1. You're comparing a half-percent deflation to a digit drop redenomination. You mean to suggest that because prices didn't drop proportionally when the value of a dollar increased by a miniscule value, they won't drop proportionally when the value of gil increases to be 10x as valuable. Do I need to say more, or do you see the extent of this flaw?
2. I never said they'd necessarily drop to exactly 10%. I'm only sure they will drop, and they will drop significantly in general. I'm also pretty sure no item will be worth exactly 10% of what they are now to match. Again, so much more than the redenomination is working towards the value changes in ARR. However, to suggest that while gil becomes 10x as valuable items will barely drop in price, and to place greed as the primary reason.
As for the segment I bolded... it shows a chink in your understanding of this redenomination quite clearly. The value of 20g in 2.0 is the same as 200g now. If they mine to sell them at 200 each now, they won't have any trouble doing it for 20g then. If the price is different from 20g eventually it will be more due to the changes in gathering effecting the rate at which silver or is obtained.