In a recent WHMCS update we were provided with the ability to enter different pricing cycles for product addons. This is great! However it as resulted in the standard cart orderform not behaving well. Steps to reproduce:
Configure a product with annual pricing only. Configure its addon to both have Monthly and Annual pricing
Place an order with the standard cart orderform with the product set to annual pricing.
When configuring the product, the addon will show its monthly pricing, yet when you add the addon to the cart, it will show annual pricing (bait and switch!)
At bare minimum, the order form should dynamically change the display of the addon pricing (on the addon itself; where the title and description is) based on the parent product's selected cycle.
Optimally I would much prefer that the addon have a selectable drop down so that the buyer can choose a different payment cycle for their addon than the parent product, but that it would default to matching the cycle with the parent product.