Random Contract Question

[Shudeye]

Apologies if this is a silly question or one that's already been asked.

Do we know what causes contracts to be so all over the place down the line? I've used a couple of rosters recently that are pretty accurate for their time periods (at least to me they look to be or are realistic enough) but I just notice a couple years down the track some players expected contract amounts are just ridiculous, they're almost what they'd be worth at their absolute peak. Even recently Steven Adams went undrafted and was in FA with around $18m expected when he's like 75OVR and literally gone undrafted. This is me with the cap turned down too to match the time periods. I'm assuming there's some random attribute that's been missed when the person's edited players or something because nothing about their stats suggests they should be on good cash yet.