error with counting prices

[medesign]

on the web I am working on (www.vcelysvambroza.sk) I have problem with price counting on product page.

 

 When I select different attribute (weight), prices are counted incorrectly. 

 

example:

Basic honey price is 4,19€ and when you get different boxing (350g) you should get + 2€ price. In CZK currency it should be (4,19+2) x 27 = 167,13 CZK. But the price is counted like this: (4,19+2x27) x 27 = 1571,13 CZK - the price is too high and incorrect. Could anyone help me with this?

thanks a lot.