I’m not familiar with the Rab products since I’ve never owned/used them. I will make a suggestion for several alternate products I have extensively used and that definitely perform to perfection (and are considerably less expensive than the Rab prices of $175 and $65).
I urge anyone interested to take a look at the website Wiggy’s: https://wiggys.com/footwear/socks-liners-booties/
All the Wiggy’s products are lined with a proprietary synthetic insulation (Lamilite) that is impervious to moisture. If it gets wet, it doesn’t affect the warmth. It dries quickly (if worn in the sleeping bag), won’t absorb water or your perspiration and become compressed and useless. Several of the Wiggy’s bootie-style items also have a sufficiently durable sole to allow using them outside of your tent for night pitstops and so forth. The prices range in between $25 up to $60 and there are five different variations in that price range.
Separately, although not intended for use in a sleeping bag, Wiggy’s also sells a great product called an Overboot. It’s a nylon insulated zippered cover with a rubber sole and is designed to pull on over hiking boots for added warmth in static circumstances (think stand hunters, or sitting around the fire in camp). These sell for $115.
(Disclaimer: I have no affiliation with Wiggy’s, other than buying and being a convinced user of their products for over 30 years.)