E.g. "It can't be 1000 USD/BTC today since it was just 130 USD/BTC 2 years ago"
I think, that is a pretty bad way to look at it.
The best way, I can think of, is what has the price to be, when a certain amount of people use it. Imagine in 10 years 100 Million people worldwide are using Bitcoin in some way(I don't want to discuss, if that is a good estimate, since the title of the topic is "if it succeeds"). Looking at the current market cap of ~$ 3 billion, that is just not enough. That means that everybody can just use an equivalent of average 30 USD.
Any other suggestions on how to determine a good price?
You see .. that's the issue mate , everyone look at the price and they want to get rich between night & another just like that .
which is wrong ... a good price isn't what makes us rich but it's stable price . Let's say ~300$ for three months . that's stable then it's good . even if it was 1$ .
Most of people don't give a shit about Bitcoin being annonymus or fast or without fees they just want to become rich. *facepalm*
that's my opinion
Good and a stable price of 1million USD/btc