> Why would unbundling without rate regulation be bad? > The network owner could set the wholesale price at one that is still profitable, no?

Yes. For example $10,000 per month.

I'm not trying to be clever here. The ISPs seemingly don't want to lease out their lines, or else they would probably have done it already. So if we wish to force the ISPs to lease out their lines, we will have to set a maximum price, either explicitly (as a dollar value) or a price that is somehow related to the costs incurred by the ISP.

That's a good point.

So then, how did unbundling + price setting negatively impact the expansion of telephone lines?