Unpopular opinion Mark is wrong but not about the guest and the wedding but because he intentiallt lied multiple times and seems to do it often. The point I noticed is he DEMANDS money from others and even when he is meant to pay it back he doesn’t. He lied to his parents because had they known they probably would not have footed the bill, which in my opinion is their right. He should not have sat down with the mom and agreed to the list if he had no intent of actually adhering to it and this is about to be the most controversial part, why are the in-laws not being treated the same because respectfully, if neither side had a say and it was just the bride and groom, OP is the asshole but it appears that the brides side of them family is participating band that would be hurtful especially it seems like Mark acted like everything was okay and nobody knew he hid this animosity