What is the value of Marvel Comics 1970s?

It is difficult to answer this question. The value of an old copy of a magazine is determined by how much collectors want it: is it rare, is it important in some way, is your copy of it in good condition, etc. I do not know if your magazine is considered rare or in demand, nor do I know if your copy is in mint condition. The best thing to do is go to a site like eBay where magazines are frequently bought and sold, and see what the going price is for a magazine similar to yours.