Hi,
This must be related to virtuemart configuration. Navigate to "vm backend >> user group" and click the "anonymous" group (which is for non-logged-in users) make sure "show price" is enabled.
Also, open any product in the VM backend, look at the price column. On the right hand side of the price column, there is a dropdown where you can define a user-group for that particular price. "Everybody" or "all" should be selected in that dropdown (unless you want to offer different prices for different user-groups)
Regards