Conte is making the squad his. He's gotten (or getting) rid of all the mourinho players and bringing in players he has clearly asked the board for. I imagine he has asked for more players and I'm sure the board are trying to get that done for him. But we are also, at the same time, trying to run like a business and not just buy players with no look toward the future. That time has passed for Chelsea...our ambitions in the transfer market are in the second tier now. So this is the frustration...I think Conte is happier with the players he has to suit his starting 11, but he knows there is absolutely no depth so he's asking for more players/upgrades and the board is like, well OK we will try to get them but we will not overpay so prepare for some squad filler type players to come in if we can't get the ones you want.
It's as if Conte wants to completely overhaul the squad in a matter of one transfer window...that simply cannot happen.
With regard to Matic and Costa, these two players wanted to leave. They were never going to play for us so we may as well sell them now and move on without them, rather than keep them in the squad and always wonder and have them lose value.