I couple of questions HomeGrown,
Is he a seasoned vet and are you a relative newbie? or are you more a regular and he a newbie? It seems like with a childish response like 825! Now go away already! he is not a professional.
My hunches are, he is a seasoned regular (although not a professsional) and you are bidding on units in his "sweet spot" thereby creating competition for him. In smaller markets, just showing up to certain auctions is infringing on someones sweet spot. You also stand out in the crowd, so you might be drawing more attention then normal 6'4" tall, 350 lbs.?
It's typical for vets to try to single a couple of newbies who they think have potential to be long-term competition and try to weed them out by running them up. It's all fair as far as i'm concerned but the "Now go away already!" is a bit much. I know you have to fight with the ammo you got, and you said you bid as high as your budget would allow, I would just suggest keep doing what your doing, and when he bids on units you run him up.
The one sure fire way to get old-timers and newbies off your back is to make them pay big time on everything they bid on. Yea, they might drop a few units on you, but just smile and keep coming back. The other way to send a meesage is to go BIG on some units, even ones your nemesis isn't bidding on. This is a gamble, and you have to be willing to lose some money, but it sends a clear message that you have money to spend (and lose) so 1. you can't be intimidated by being run up, 2. You can make life miserable for everyone else.
The bad news with this technique is you will lose money, and potentially a lot of money. The good news is you should be able to get your nemesis and other knats off your balls within a couple of months instead of induring the thousand cuts of death from this guy and others for the next year, 2 years, however long you plan to do this.
Here is what I would do to your "friend". Next time he is bidding on a unit, assuming it's a slow auctioneer, walk right up to him and say "Oh, your bidding on this unit?" Then drop the maximum you would be willing to pay for the unit right there. For instance say the bid is at $200 and the most you would consider paying is $800, then walk right up to him and bid "$800!" Now he has to go $825 or $850 to win it. Don't do it every time though, do it a couple of times then leave him alone cause he will try to drop a unit on you. Now he never knows when you are going to blow the bid up!
If he's got any sense he will move on to messing with someone else.
Good Luck!