First off I 100% believe Bitcoin will go to 100k+.
That being said when bitcoin was at $40 and had potential to go to $100 would you have bought? Of course you would have! If(when imo) Bitcoin makes it to 100k you’re still early even at today’s price.
Just because something is 40k doesn’t make it expensive. You have to see the potential as with anything in life.
Also you don’t need to buy a whole coin nor do you ever have to own a full coin. Buy as much as you feel comfortable with.