I'd keep it 1 pray as it surely won't up it's price since it doesn't take long/the buyer could do that himself if he wanted. If it stays 1 pray for now though, people could build it into a better/lower combat F2P pker or staker.
Anyways, pretty decent obby mauler you got there.
You could get anything from 25-50m OSRS gp, or $70-130
If it has 55 slayer, obviously more or less. It also really depends
on if you find a good buyer, who's looking for an exact build like this.
EDIT: Lol, yes. Either put that money on a secondary/mule account or just sell it here if you want to quit. That's a good $230-$250