no it means that in order to high alch you have to buy nats. which cost alot. and so say you make 1m off of high alching something that was 1k each and you had to buy 1k of nats to get that. then you spent 400k to make those 1k of items turn into 1m so essentially you only made 600k off of what you were trying to make 1m off of. you get it now?