OK – figured it out. This is the same issue as https://ww.wp.xz.cn/support/topic/option-pricing-amount-disappears-after-adding-to-cart/
In my case the contending plugin is ‘VarkTech Pricing Deals for WooCommerce’
Thankfully we’re not using ‘funky’ coupons right now, so I just disabled it and things showing up fine in the cart now. Hope this helps others. essentially – any plugin that intercepts the cart could interfere with any pricing alterations on products.
