Title. Don't care if I'm under, your opinion is your opinion and I'll respect it but I'll tell you why I see this trade as fair.
If you think about it in terms of bucks (which I'm aware that not everyone does), 9 fossil eggs costs 6,750 AMC. If you buy AMC with robux, you have to buy the following in order to get 6,750 AMC: 1385 Robux (for the 3000 AMC option), plus another 1385 robux for the same option, plus 280 Robux (for the 600 AMC option), plus 74 robux for the 20 AMC option (three times). That total of robux equals out to be 3,124 robux. For 3 ride potions it's just 450 robux. For 4 Ride potions, it's just 600.
That's how I view it as equal/over. Sorry if you disagree! :)