Teaching gratitude?

So my son is almost 8 and he’s ALWAYS been the sweetest most appreciative easy to please child ever. His dad and I separated when he was 2 and we have both remarried since and all is well. However…. His dad and bonus mom have more money than my husband and me. We have more kids together than they do and they’re all younger too and REALLY hard on clothes and shoes (besides my 8yo son, he’s SO neat and tidy and careful) so we don’t like to spend tons on brand new things for that reason really. But his dad and bonus mom do. Anyway, I’m not sure if it comes with age and he’s wanting certain things because of kids at school or his step siblings on his dads side or what but lately he is so hard to please. Like almost spoiled. We do week on week off and EVERY time he comes back he has a snooty attitude and if I’ve bought him shoes (we do buy shoes brand new and undies and socks of course) he’s never really happy. He will say he doesn’t like them or didn’t want them etc. I just got him new chacos in his fav color and he said he would’ve rather had crocs. I’m glad he’s honest with me so I know what to get instead but at the same time I wish he didn’t say it so snooty lol. I try to raise them all to be appreciative children and he’s the only one that doesn’t ever really say thank you. It just kinda makes me sad. I’m glad that he gets all this nice stuff at his dads but I feel like he kind of looks down on me a little because I can’t do as much and my house isn’t as nice as theirs. I dunno. I’m just venting I guess.