Can't Use Child Themes Question

I have just been told that the child themes are basically of no use to me because I have a non responsive classified press theme version 7.1.4 and will have to pay for a new theme at a discounted price of $59.00. $20.00 less then what I paid for the current version that is basically of no use to me anymore without the use of the child themes. Not understanding why I need to pay again when I was entitled to free updates, free child themes, and free support? Can someone explain this please? Thank you it would be greatly appreciated.