50% less seems low. Everything is a negotiation. Remember this. If you think you're worth more (and you obviously are since you make 2x of that offer right now)

50% less seems low. Everything is a negotiation. Remember this. If you think you're worth more (and you obviously are since you make 2x of that offer right now), come back with a counter offer that's 50% more than what you currently make. If they say they can't do that, then you can always counter back and push for more options in exchange for less cash.