It depends on what you want, because i believe that if really you want to make a profit in any trading you most not start with higher price, at least you will be targeting the figure or the value that when you open trade when negativity come it will not lead you into lost, so the factor of determination is dependable on your target.

When you do say low price, then how you do able to determine?

Via trading indicators?
Via Hype or people been recommending and saying around?
Via emotion or intuition?

You are the ones would really be deciding on when to enter.Yes, this market is truly unpredictable and totally random which it would be
sensible and would be much recommended that when you do consider on buying back then analysis should really be attached to it.
Never ever consider on making your emotions plays a huge role when making choices.