No one has any excuse not to buy Bitcoin because of it's price.
If you don't have the money to buy a full Bitcoin at once, then use DCA and you'll achieve it after a while of consistency. We are encouraged to use any accumulation strategy that sure suits our ability and the quantity of discretionary income available to us. Hopefully, you can follow up your DCA and save for the dip alongside it and possibly during dips you can buy a full Bitcoin or a good quantity at a much reduced price while you continue accumulating periodically to reach your accumulation target within your holding period.
Giving yourself excuses instead of buying may see you not accumulating Bitcoin at all and possibly regretting your over skepticism on the long-run and wishing you were more practical with your Bitcoin involvement.
A person should invest when he thinks it's fit for himself.
Only by holding rightfully and accumulating consistently one can achieve results in the end.
I think it will be proper if I say a person should invest in bitcoin when they have the discretionary income to do so that is money that is not for daily expenses. Although some people can raise discretionary income ones they can be able to discipline them self to quit some habits and as reducing their daily expenses making it possible for them to have discretionary income or more as those money that use to lavish on irrelevant things can be Channel into bitcoin investment.