Not sure if this a bug or an Easter egg but when I go to the buy form and choose the Ultra version the price always jumps by $10 when I pick it ($89.99 vs $79.9

Not sure if this a bug or an Easter egg but when I go to the buy form and choose the Ultra version the price always jumps by $10 when I pick it ($89.99 vs $79.99, $39.99 vs $29.99) ;-. Is this tiny surge pricing? Edit: I only get this behavior on my phone.