I made a spreadsheet that you can use to calculate if buying raw materials will net you a profit if you craft them into potions and flasks. It takes the 5% Auction House cut into account. It's on a per item basis so if you have a rank 3 recipe profits might be higher than expected.
It looks like this:
You should be able to create a copy of the spreadsheet by clicking this link.
It looks like this:
You should be able to create a copy of the spreadsheet by clicking this link.