Instead of slowing TSM down for certain players, just tax them exponentially. For example, if you sell or relist more than 10 times per day, every listing fee gets increased to 500%; at 20 transactions/day the listing fee is 1000%, at 30 transactions/day, listing fee is 2000%, etc. without a limit on the listing fees.
This will prevent constant undercutting by brutosaur owners and ensure that professionals can only participate in several markets instead of dominating every market and thus allow smaller players a chance to compete better.