David.   This is going to take some Javascript to get done.  But not to worry.  I don’t think it will be that tough. 

For starters - you should go here:  http://help.skuidify.com/m/getting-started/l/151288-copy-paste-individual-sample-pages-you-can-see-i…
This is a set of starter pages.  Look for the opportunity detail page there. 
Note that there is a link to a javascript file that you will need to set up as a static resource. 

The javascript in that page takes the product price and prepopulates it into a line item based on the product selected, and calculates total price. 

In your case,  I believe you’d need to determine what pricing tier you were using and use the appropriate field as the basis for your calculation.  A little more complicated,  but not bad… 

Hopefully that gets you started. 

Hi Rob, as someone who is not familiar with javascript, would this be something you think I could tackle alone? If not, can you send me in any direction to get someone to help write the javascript code? 

Thanks for your reply! 

Anyone on the community want to reach out to David to offer some help? 

David, the javascript here is attainable, but there are some wrinkles associated with the Salesforce opportunity line item process that you need to take care of.  We’ve done it in the file I sent you,  but not for exactly your scenario.  

David I can help you with the Javascript just try to post as detailed a description as possible of what you’re trying to do. Videos and screenshots are really helpful as well.