OP, once you determine IF Marriott will list them, I would just do a comparison of net to you between Marriott as the broker vs open-market sale, e.g.,
Maui 3BR Lahaina(extreme example I suppose)
- Marriott lists at $76K, at 40% commission, you would net $45,600
- Timeshare Broker lists at $70K, sells at $60K, at 20% commission, you would net $48K (While some brokers are at 25%, at this price point, I would assume there is some negotiation room, $5K sale price units, not so much.)...but sells faster at lower price, presumably.
- Redweek Full Service listing with their broker at $70K, sells at $60K, at 3-20% commission, depending on if another broker represents the seller, you would net $58K to $48K, also selling faster than Marriott.
I see Redweek listings for Legend's Edge for $1500 on Redweek, so guessing that's your best bet, or eBay, just to get rid of it. Not sure any broker would handle without a minimum commission charge on top of the sale price.
Surfwatch is more likely to fit the model above.