But you already skip several rather crucial steps that an automated program does for you. When a normal player searches the neutral AH without any addons he/she needs to do the following:
1. With the mouse select the Search button (assuming the name of X item being transfered is typed pre-search).
2. Scan the number of auctions available.
3. Select the auction you wish to purchase manually with the mouse.
4. Move the mouse down to Buyout and left click it.
5. Move the mouse up and confirm the transaction.
If you can do this in less than 1 second then I welcome you to the book of Guinness world records.
If players are allowed to tweak the game this much, what will stop them from doing it on other things? A few examples can be Charging in combat as a warrior, shooting without breaking stealth from Shadowmeld as a night elf hunter, using double trinkets or multiple items and spells with shares CDs at once etc. Where will the line be drawn here? You cannot argue that it is exploiting because these examples above do just what the addon on the auction house does, it tweaks things to allow you to bypass other mechanics and/or change the way the setup looks. You are not able to search the AH every 0,1 seconds without an addon, but with one you can. You are not able to buyout an item using the steps above in less than 1 second without an addon, but with one you can.