Unfortunately no. Any high value item that you list on the market will be an open door to muggers looking for a tasty snack. The reason you are repeatedly getting hit is because even though the money is hidden now, your online activity opens the door to the possibility that you might try to move it. If they catch you with the money on hand, they get their piece of the cash.
My suggestion to you is use traders. Find a reputable trader with a good friends to enemies ratio and sell items to them. If you'd like a recommendation you can DM me. (I won't list here because I don't want feelings getting hurt lol)
Also, look for a faction to join. You're missing out on a big part of the Torn experience. The more respect, the better, I'd suggest looking for 1 million or higher.