This was something that the Apollo dev (and a few other apps) were interested in, but the timing was just too sudden to make work. Specifically for Apollo, they had been selling year-long subscriptions for $12/year. With the API pricing change happening on July 1, that meant Apollo would have to continue to offer up to 11 months of the same service, at the same price (since users
already paid for it) while operating at massively higher costs.
Christian even said that if Reddit had given app developers longer -- maybe six months to a year -- it would have been tough to change the business model, but not impossible. With this timetable, he would have had to come up with something like $500k in 30 days just to cover immediate costs, which was obviously impossible.