Here's a clean link to the one you are looking at:

https://www.amazon.com/dp/B07LC4NK2G/

R-values on sleeping pads are so low that it doesn't make much difference, especially with lows of 40 deg and the protection provided by a sleeping bag. As long as it gets you off the ground and is comfortable enough that you can sleep, it doesn't matter.

Get one that is within your budget, but if you want a really cheap one, say under your $50 budget, choose one that is CCF rather than inflatable for reliability.

The review of the one you linked to stating it was purchased for a 12-year-old is probably a realistic assessment:

We have 3 Klymit pads for backpacking and needed one for our youngest child. This is comfortable, took more breaths than the Klymit to blow up, noisier than the Klymit and not as comfy. It will work for a 12 year old, not convinced on the longevity of the pad. Weight was not bad, but did not fold into as small as a stuff sack as the Klymit did.

Kelty is a decent backpack-I used a Redwing on a 12-day 120-mile trip. here’s a link to Amazon but it was actually only $110 for the 65 L; I used this pad on that trip, $30 and it was outstanding; of Amazon stuff, that might’ve been it. I found Columbia pants and zip-off pants reasonably discounted on Amazon, but I don’t see them now