I’ll start off by saying, ad CTR’s are much higher than sponsorship CTR’s, and I’m not sure which one you were referring to in your reply. It sounds like you were talking about ads, (correct me if I’m wrong on that.) In the case of ads, you’re right that the CTR should be much higher than a sponsorship since the number of impressions for ads is much lower than sponsors. (We’re taking a difference of thousands vs. millions of impressions!)
It appears to me that the poster is using sponsorships, not ads. For sponsorships, I like this range for guidance: Thoughts On My 10 Robux Sponsor? - #17 by zaydoudou
The poster’s cost is about 3 Robux per play, which is pretty good in my opinion. With such a low cost per play, I would imagine that the poster may have been profitable, (assuming the game has concurrent players & is monetized to some extent.)