Why is no one doing anything about Forza Horizon cheaters ruining the game?

I am currently playing FH3 (I also own FH4, which is also starting to be targeted from what I hear, but want to complete part 3 first).
In recent days, I noticed the same few people always winning every auction I tried to participate in, and now all the cars available (Forza Horizon Editions) are sold at the same, eyewatering amount of credits (by the same few players) which is impossible to earn playing the game as intended (1 million takes a while to earn legitimately in FH3, but the Jaguar XJ220 HE is only available for 20 million credits now - until about 2 weeks ago, I frequently saw it being sold under 1 million, but now the same few players are running multiple auctions at a time, all for 20 million minimum bid, which is also the maximum possible to set).
This is ruining the game for everyone playing legitimately - when you can't access the top cars unless you cheat, it only encourages more cheating.
Besides, it's not normal for the same player to have the same horizon edition car on auction 5x concurrently, all always at maximum price.
An easy solution would be to ban all players with a 999.999.999 credits account, and especially all players selling the same Horizon Edition cars in multiple auctions at the same time (always at prices above 10 million credits).
On a side note, please enable the purchase of DLC to players who already own the game. It is like playing a broken game when half the available vehicles are inaccessible, as are major expansions like Blizzard Mountain (I'd happily pay for the expansions). Thanks.

:)