I'm not really sure how to check legitimacy of the shoe, but the Lo's were 90-100 retail and the Hi's go for 100-110 retail depending on where you get them. There are still plenty of sites that have them if you don't want to take the chance with fakes.
Well they look beat to shit already so I can see why they would only want $25 for them. Have them take a picture of the box and I can confirm whether they're legit from that.