My question is based on the fact that there are many hidden costs , health ins workmans comp unemployment etc etc . Can you calculate for me an estimated cost for an 18 dollar an hour employee. It is my belief that I can save the company I want to work for 5,000 dollars a year while I almost double my net pay. If they hire me as a subcontractor rather than a regular employee

Well let me see, you will not have any workers comp coverage, you will not have any unemployment insurance to cover you. You will not have any health insurance ( have you ever gotten a price for individual policies)
And you will have to pay an additional 7.5 percent in taxes on your income for your share of the self employment ( social security) taxes.
Also there is holiday pay, vacation pay

So unless they increase you current pay scale by a higher amount than you make now, you will have a net income a lot less if you try and have all the same benefits paid out of your own pocket.

But just their share of your social security will save them 2800,

There are also some "requirements" that have to be met in order for the employer to classify you as a subcontractor. You could end up with a lot of headaches if it isn't handled properly.

Employee vs. Subcontractor - Bookkeeping & Quickbooks