Hi thegoldenband,
Lock n Chase can be frustrating at times, but then a lot of the best games are - it's what keeps you coming back to try to beat them next time!
As you say, the bonus cash appears at regular intervals and is dependent on the number of gold coins you pick up. If you're finding that the cash is appearing when you don't want it to, try to stick to sections of the maze that you've already cleared until you've drawn the cops away from the middle - they will move out eventually, you just have to tempt them towards you. Once the coast is clear, pick up some more coins and then make your way to the centre.
It's interesting that you mention the cleverness of the cops. You're right, they are are lot craftier than many in similar games of this type (personally, I've always found the red cop to be the cleverest, followed by blue, yellow and green, but that could just be my imagination!) but there are ways to trick them. Making use of the lock feature is the most obvious way and is absolutely essential to doing well at this game. Locking cops in the top left, top right and bottom left corners will make it much easier to get around the maze and collect the bonuses, especially if you're able to lock two or more of them in at a time.
I hope you don't give up on it - personally, I think it's one of the best games on the Intellivision and well worth persevering with. I hope you stick with it.
Good luck