IIRC, the problem last time was that renting a truck is an expense, so you have to combine as many deals as possible for maximum efficiency?

That's the wrong way to look at it.

When you bought your car, you saved thousands by not buying a truck, right? And over the years you've owned your sensible car, you've saved money on fuel and repairs, right?

So, with all that money saved, when you do need a truck, you can man up and rent one. And if you need one the following weekend, you can rent another one.

Don't think of that one-dollar-per-mile U-Haul bill as adding to the cost of the pinball machine. Think of it as adding to the cost of your sensible car. It's still cheaper than owning your own truck, right? Then relax.

Low-ballers are betting that the seller is desperate, right?

With the way pinball prices are running these days, what are the odds that the seller is desperate?

Then why did the seller say "to low"?

Your original offer for the "needs work" was too low. (You say this yourself.)

When you made the "combined" offer, did you up the price you were offering for the "needs work"? Or did you use your old offer, but expect him to jump on it because you were also going to buy another machine?

This is the clearest answer.

There's no "etiquette" that requires a seller to haggle with you, or "counter you", or anything else like that.

If the poster thinks such etiquette exists, that would explain why he's constantly surprised.