Chelsea recently rejected a loan bid from Bayern Munich for Nkunku. The club wants to keep Nkunku permanently, which is why they're not willing to negotiate the price. This is also the main reason why Garnacho's transfer from Manchester United is taking longer than expected.
Manchester United values Garnacho at £50 million, but Chelsea is hoping to get the deal done for around £30 million. Garnacho is eager to join Chelsea and talks between the two clubs are ongoing. He wants to move to Stamford Bridge, but the transfer is stuck due to the Nkunku situation.