There is 3 ways how the item going to be sold in the Marketplace after someone registered it.
The way is selected randomly by system, so u cant influence on it somehow.
After the server announcement that item u want, is registered on the Marketplace, will appear for the Bids in about 5 min. after. (You have to spam Refresh to see the item in time)
When it finally appears for the Bids, there is about ~1 min. for the Bids. The item will be sold to a random person between those who Bid it in this ~1 minute. If no one Bid, item just will be available to buy for everyone.
Second is the Auto-Purchase. The difference between first one and this is that item is not going to appear at Marketplace for Bids at all. It will be sold instantly after its registration on the Marketplace, randomly, between all players who is Reserved item by Auto-Purchasig.
3. Max Bid Price
And the last, third, is the Max Bid Price. Very simple - item is not going for bids, just like second way. The player who Max Bid with the highest amount of silver will get the item.
!NB Remember, server announcement about the item registration on the Marketplace means item is going only for Bids (First way). There is no server announcements for Auto-Purchases and Max Bids. So if you see the announcement - go for it. It will appear in about 5 minutes after.
**5 minutes rule is not working for Pearl items (often it will be next minute after server announcement)