Actors are paid to act; any agent can tell you that the script is the least important part to them. When it comes to the principal cast (which the sales and financing are predicated), unless I can call the agent or manager directly myself and verify, there is no real attachment. The exception being a Spielberg or a Scorcese whose stature in the industry could reasonably facilitate any star interest.
Many a time, especially in a case involving a supposed seller who is either a fake seller or does not actually have the supposed crude in hand yet, or, an unscrupulous aspiring seller's agent or broker who actually has not acquired a crude supplier (seller) yet, buyers may issue an LOI only to find out that there is no seller on the other end. This happens a lot in situations where you have an hungry agent or facilitator who is still struggling to get a real supplier, and by extracting this LOI from an unsuspecting buyer, this facilitator can commit the buyer only for him then to start hustling to find a seller or supplier.