Yes but that's a bit of a generalisation, for the most part it's going to be on items starting 20-30 pounds or more, and bidding multiple times does not mean paying more than I want to pay, which is the main point. Sure, I might have to pay up to the next increment (and we're talking a pound or 2 tops), but that doesn't mean it's being sold at a price I'm not happy with, as it's inside of my max.
This also assumes bids are in the increments of the minimum amount. If I would pay 100 pound for a coin and it's starting price is 15, I can put 15, 16, 17 then 100, it's not going to affect the outcome all that much if someone comes along with 20.99. It's one of those things that you can't prove though, maybe it dissuaded 10 people from having a look, maybe none. Maybe, like you say, someone came along thinking they could be smart and my own plan actually elicits a new bid!