"Or do brokers only use comps with financing to present value to owners when they do listing presentations?" - I doubt brokers take financing into account unless a comp is abnormally low (cash or other discount) or high and they start investigating.
"Are we saying financed apartments are worth more? " - not in all scenarios, but most I would say yes. Depends on how much the buyer wants that property and the competition that exists at the time of bidding. But in general, all cash buyers do 'expect' a steeper discount for offering a smoother/faster transaction with less risks. What is that worth? Depends on so many factors it will be impossible to measure: sellers desperation to liquidate, the product at play, the pricing.
This is an obvious one --> All cash as an incentive is most effective when there are no other competing bids. If there are competitng bids, a review of the strength of each bid and the difference between the bids is warranted. I would think once you get past 1-2bps, the decision gets easier for the seller