DXP merchanting

Well I have a query on some items, since a lot of people were making herblore potions, the price went down a few k under ge mid. So my friend has piles of antifire 3, super restore 3, super attack 3, etc, etc. Now I suggested for him to sell them all now while he is arguing to hold them. My argument is that a lot of people are doing herblore, alot of people have the same idea and thus their price is only rising due to people trying to stock them. Thus I told him to sell it now and make profit and be done with it. He said but after dxp the price will go back to its original ge prices and he would make more profit. He has invested 362m in this and said he doesnt mind waiting a month to sell them. Would this be worth his time and investment or would he make more with that 362 used somewhere else? (depends if he sells in a few days, a week or a fortnight or a month)

While it's true that alot of people are stocking the same item, good profit can still be made.
For this 2x xp alot of people invested in supplies and it still worked out nicely.
You are right though that if it has already started rising the longer he waits the bigger the risk. He shouldn't get too greedy with this. Better sell a bit early than risk missing a peak and item already crashing heavily.(especially with 362m in potions. I suppose that's a pretty big stock).

^This I think should be true generally. But potential for pretty safe profit is still there. Would have to see items' graphs(their price before bxp) and track the item actively every day with PCs to try and sell at the right time.