How to deny a "Ready willing and able Buyer" -- RE AGENT

[Devin Mann]

I am listing a house thats about to go on the market.  i am listing the house 10% below market value and hoping to create a bidding process so they can make better gains and sell it faster.

value is 320k,  and listing it at 280k.  If someone comes in with an all cash offer at 280k and says i will close on the buyers terms how can i reject that offer?  That would mean they are a "ready willing and able buyer".

So my question is, what can i write in the "additional provisions" on the mls to say that the price is starting at 280k but wont be sold at 280k