bidding platform to auction niche products

says I want to sell my Rolex watch, I post to Rolex watches facebook or telegram group. I'll get tons of direct message and asking for the best price. I'm thinking of building a bidding platform to help the selling to sell the item at the highest price.

the seller is free to post the items
the buyers can bid the items
the platform charges a percentage of the item price after the bidding period ends

What do you guys think?