@Maus0728, I have been regularly depositing and withdrawing Bitcoin in Roobet. As far as I have seen, the fee ranges from 0.5$ to 3$ depending on the network traffic, but I have never seen such insanely high fees for withdrawal. Not sure from where you heard that.
Same as mine. Whenever I visit the withdrawal form usually it's just 0.5usd, the highest that I have ever seen was about 7 USD I guess.
And I don't think that the withdrawal fee will is directly proportion to the amount of that you are wishing to withdraw.
I am sure there are times when withdrawal fees are big compared to a year ago for example, and in some places it is quite high, for example some exchanges charge as much as 7 dollars for example, which if you ask me is quite high.
For example, I wanted to buy something from a game and it used either coinpay or coinbase I forgot which one and it took 7 dollars for transaction fee alone, which is huge.
However 150 dollars is something I have never seen anywhere including here. Max you could see anywhere would be around 10 bucks at most, if you see something bigger know that something is wrong and do not do any move, you may want to get out and do it quickly so you may rush it, but if you see 150 bucks just stop, wait and see what's wrong. No place charges that much, neither here nor anywhere else.