Auctioning claim goes to debt If not enough cash. It also does not increase black market claim cost. Thus it SHOULD overbid compared with black market cost.

I think it can also be realistic in mimicking human behavior for lower difficult AI. I actually got my brother to bid $24,000 on a regular claim that was ~$3,000 on the black market because he got too focused on beating my bid and he forgot to check the price. He had to bow out early because that crippled his early game.

not a bug, I do the same thing, and I'm not alone. Since currently you cannot just take out debt, then debt money is sort of different from actual money at hand. At first actual money on hand is worth much more, however as the game progresses, your debt is going to start to bite you as the interest ramps up.