Complex sentence: When the machine was eventually delivered in 1985 the delays had been so long that much of its performance benefits were due to the fast memory, and the machine only really made sense to purchase for users with huge data sets to process.
Split into simpler sentences: When the machine was eventually delivered in 1985 the delays had been so long that much of its performance benefits were due to the faster memory. Purchasing the machine really made sense only for users with huge data sets to process.