Hello -
Actually, there IS a solution for this! You can do "price overrides", or "=" pricing of custom fields using our integration extension, Breezing Forms Custom Fields for VM2.
I don't believe you can do this (yet) with native VM2 custom fields. You may want to check out our extension then, because it gives you the ability to use any style of fields supported in one of the best form design components for Joomla, Breezing Forms by Crosstec.
Our Breezing Forms Custom Fields extension offers a viable approach for complex custom fields, as long as you don't need parent/child products or to track stock by each of the options. It does NOT track stock by each option selected.
This extension seamlessly integrates a completely custom Crosstec Breezing Form into the custom field area of a VirtueMart 2 product. Because BreezingForms is a fully featured form development component, this means that you can do all those great things you expect from best selling form design software (including checkboxes), then use that form as the way to capture product options and attributes for a VM2 product.
If you think this sounds like it might help you, here's a link to our documentation to learn more:
http://docs.polishedgeek.com/wiki/display/BFCUSTOM . There's a also a YouTube video there on the doc homepage that explains it a bit more.
You can learn more about the form component our extension integrates here: Crosstec BreezingForms
http://crosstec.de/en/extensions/joomla-forms-download.html (You have to have both VM2 and BreezingForms to use our extension).
The plugin has been vetted by the VirtueMart team and is available for sale on our website or here on VirtueMart.net (
http://extensions.virtuemart.net/extensions-virtuemart-2/breezing-forms-custom-fields-plugin-detail)
I'm happy to answer any questions you have. Feel free to pose them in the forum here, or if you would prefer to discuss your requirements more privately, just open a ticket:
https://polishedgeek.com/clients/contact.phpHope this is helpful for you.