Does it make any sense to buy Bitcoin now? Isn't the price too high?
Some say that Bitcoin will fall. Then it doesn't make sense.
Some say that Bitcoin may get to 20-20k before the year ends. If you believe them, you better buy asap.
We can't tell what's going to happen. I believe that even if it may fall, it will also recover to even higher levels.
Will it ever offer 30 000% returns?
300x returns? No. But some say it could easily reach 1 million until 2020. That's 58x, not very bad.
However, if this is what you expect, you better stop investing now; with such expectancy you'll fall for Ponzi schemes and you'll lose your money.
All in all, if you believe that Bitcoin is a good project, if you believe it didn't reach its maximum potential, then you can buy.
If you are just a speculator wannabe, you have a lot more to learn before starting to work on real money.