In the case of R.E. Davis Chemical Corp v. Diasonics  826 F.2d 678 (7th Cir. 1986), 924 F.2d 709 (7th Cir. 1991), a trial was needed to establish that the plaintiff had the capacity to make an additional sale (since the goods were pretty rare), and that it would have been profitable for the plaintiff to have made a second sale.  Sometimes it is not clear if a seller is indeed a lost volume seller.  It's important to remember that although § 2-708(2) allows for recovery for lost volume sellers, the fact that the sale is indeed lost volume needs to be established.  It's never as cut and dry as the Neri v. Retail Marine Corp. judgment implies.

• Since the extra legal expenses required to establish the damages can be greater than the actual damages, it makes no sense to have a trial. Neri v. Retail Marine Corp. just makes the assumption that you are a lost volume seller if you are in business.  That simplifies the system, even if it isn't always technically correct.  Courts tend to be very sympathetic to the Neri v. Retail Marine Corp. decision.
• Common law courts often take a similar stance, even in cases that don't fall under the UCC (eg a house owner who breaches a contract with a housepainter).