again with the creation cost! when will you start seeing that cost of mining changes with the price not the other way around.
price goes up > mining becomes more profitable > more miners join > hashrate rises > difficulty rises > cost of mining increases
price drops > mining becomes less profitable > some miners leave > hashrate drops > difficulty readjusts (decreases) > cost of mining decreases


additionally you are not talking about "investing" you are talking about day trading here. an investor shouldn't care about these short term fluctuations. you invest long term and timing in that case is not as important specially since "investors" invest their idle money that is not in anything.