It's probably very rare the holdouts sell truly cheap. More like slightly cheaper than they could, but still at a very large profit.

YIMBYism simultaneously raises prices (presumably for the greedy developers and sellouts) and lowers them (for the noble neighborhood defenders who are forced to sell). Got it.

I'm going to ignore your presumptions (your "greedy developers and sellouts) and things I did not say (like "YIMBYism lowers prices for noble neighborhood defenders who are forced to sell"), so basically every word and try to find the spirit of your comment.

It's pretty difficult to fit a massive apartment building on a house sized plot between two massive apartment buildings. The prices you will be offered are not what your neighbors were offered. There will also be pressure on you to sell because your neighborhood is now shit. Your house prices may still, all that being considered, have massively risen since you bought the house. The property taxes also rose proportionally, sucking away your equity.

Any reply to this other than vague sarcasm?

I think the contradictions are pretty clear: it raises prices, but holdouts sell cheap; it's a shit neighborhood that no one wants to live in because it's too crowded...

And the hypothetical boxed-in holdout scenario is simply not representative of what's happening in high demand areas in the US. We're preserving laundromats and parking lots in San Francisco and Manhattan. No one is trying to build towers in the middle of suburbia.