Prices appear only on registration

Is it possible to have the prices appear only after someone registers?

Yes. In the Business edition, you can set an access level on the price of the products. If you set it to only registered user groups, unregistered users won't see the prices. Instead, they will see by default the text "Free", that you can change via a translation override:
www.hikashop.com/en/download/languages.html#modify

ok thanks a lot - I will upgrade to business in few days then

when one does this it is true that the prices only appear on registration but the problem is that those who are not registered see the word 'Free' instead of the price. I would like to replace the word 'Free' with 'Register to view prices'. How do I do this please?

You can use a translation override for that:
www.hikashop.com/en/download/languages.html#modify

thanks Nicolas perfect!