variable price, two weights , two prices, how to??

go to attributes and make an attribute for “weight” click on the little configure terms cog wheel add 1kg and 2kg or whatever weights you want different prices for.

go to your product and under Product Data make your product a “variable product” then click on attributes and select “custom product attribute” you should see your attribute for “weight” select that and click on “add” click on select all to add your weights and check the box that says used for variations. Save attributes.

Click on the Variations tab you should see your two weights, click on the little down arrow to show options, add the different prices for each one there, update your product.

or you can follow this also http://docs.woothemes.com/document/product-variations/