I can assure you that there's no improprieties going on.
Last year I went into Home Depot because I wanted to buy 10 sheets of drywall. I was told they were out and to come back the next day. The next day I went in, they were sold out again. I found out later that they were selling in bulk to their big contractors early in the morning. The benefit was being a contractor.
The MLS is just another way to market property for sale. It's not the "only" way.
I'm just wondering how you get information that the offers are from Realtors. I'm a Realtor and even I don't always know who made the other offers. Nobody would disclose that.
ultimately if the properties are priced significantly below market, the offers will ALWAYS be above list price...that doesn't mean that paying above list price is a bad deal if the list price is already below market. Put your offer in. If your offer is highest, you get the house. Ultimately, that's all you can do. I wouldn't suggest letting the presence of other offers dissuade you from making your own.
For example - if a house is listed at $50,000 but is truly worth $100,000 and there are offers of 75,000 on it...is it a bad deal for you to offer $80,000? It's worth $100,000...only way to do it is to know your market, know your comps, and make offers based on market value...not based on list prices.
Hope this was helpful!