Yes $4K is the perfect time to buy bitcoin. The problem is when, we don't know it happens. I think it's a loss have to wait while we want to invest in bitcoin.
Yes, taking the current price into consideration, $4000 seems to be the right and best price to be bought. Now we've missed the opportunity and has reached a level far away. It's good to leave that, and focus on making regular investments unlike the price increase and decrease.