Incremental price not showing on Product Details page

I've followed your tutorial on setting up Incremental Pricing and have gone through it several times, but the incremental amount isn't showing on the details page. I'm not sure if the issue is with the recordset or the code on the page.

I have two product categories, Books and CPD Courses. Books are available in two formats, download and paperback and Courses are available in day 1, day 2 or both day options. Paperback books are £4 more than downloads and a 'both day' course is £288 more. I've set up all these options as per the tutorial and I have two select lists on the details page, one for books and one for courses (using a Show If to only show the relevant select list).

I added the binding from the price increment recordset to the select list as per the tutorial, however it only displays "Download + £" or "Paperback + £" with no amount shown, therefore no incremental amount is carried through to the cart. Copy of the details page is attached.