the only hidden cost is $15 fee.
the ads on the timeshares tell you about the $195 fee for the entire week.
the ads for the hotel tell you about the $32 (might be $33) extra charge per night for the hotels.
If you read the ads before you bid - you will be fine.
kept in mind that no matter what you bid - you will be charged $210 plus your bid.
you can win auction at $211 - I have.
there is also the ready, set, go - which I haven't used. So I don't have first hand acknowledge of these.
also there is new - home away from home - might be the best yet - especially if you think you will return to WDW in a year. I have only won one of these - so I won't go further until I experience myself.
the best deals are last minute. Within 14 to 5 days before you leave. they may appear a bunch of nice timeshare.
good luck