If you actually believe that's how transfers work then you are simple.
Clubs scout players for months, even years and the bigger players will neccessitate a discussion with agents or "intermediaries" (i.e. people representing clubs unofficially so as not to cause issues for players/clubs or whomever) to put the feelers out and see if the player is interested. That player might then want to look at Houses, Schools, discuss it with his family or whatever else and the finer details of his pay packet, image rights and the agents fees.
I suspect that once a formal bid is made, everyone already knows that the player wants the move and that personal terms can be agreed. The club losing the player might then want to investigate replacements before they sanction any move.
Fact is, most of this goes on behind the scenes and the Costa thing will have been going on for ages. At the time they played them in the Champions League it was being discussed. This will have taken months to put together. Fabreags, I suspect has had his agent investigating a move for months, well aware what was likely to happen, or indeed preparing for what might happen. The Agents of these players will always be assesing what options are open to their client's even when they are settled.
Perhaps things may work more quickly when you're talking about young players desperate for a move to a big club and jumping at it when it comes along, or when transfer deadlines are looming. As it is now, why would a player not take his time in making a decision about his future when he's got ages before a decision actually needs to be made?
The sensible thing to do in this scenario is to go about your business quietly - rather than do what they did last year and have it all out in the open, which suited neither players nor the club. Hopefully they have learned their lesson from that and the silence is down to the club getting on with business and keeping it out of the press. I suspect your (and other fans) "frustration" isn't high on the club's list of concerns. These things take time and its best to do that to get the right players in.