Okay for retail you have to empty your whole entire retail store. Then, take flowers, fruit, random items and price them at 999,999 bells. Fill your whole retail (so 8 items) then when I buy all of them you refill it, again and again until I've bought enough items. So if you'd like 8m per 100. For 500 it'd be 40m. So you'd have to refill your retail 5 times. :3
And as I buy the items I will drop them outside of your retail so you can just reuse them instead of finding 40 different items.