If you don't want people to bet right before the bet ends, then simply reduce the potential winnings gradually right near the end.
This is already the case, which shows you still haven't read the FAQ.

Then why is there any worry about last-minute bidders "scamming" other people at all?
We're dealing with mid-intelligence criminals here. MP pays them "dividends" from people she's ripped off and then they slap each other on the back. Circlejerks like that seldom make sense.
All MP's 'businesses' would be in the red if they had to stop stealing. S/he managed to run a company in the real world for how long before going bust? And how many tens of dollars did he/she make in those years?
I used to know a few criminals back in the day and the attitude of MP reminds me of them. They used to say stuff like "Someone leaving a window open deserve to be robbed - the idiots!" or "What did the stupid bitch expect leaving her handbag on the floor?"
Absolutely no difference between those crims and bitbet. The thing about both groups is they prey on people being trusting. They think someone trusting someone else is a fool. I expect MP was abandoned as a child and this is how s/he gets back at the world. Fuck all these criminals. All they ever get is a very short term gain then a life full of misery.