In a way I am kind of proud that I still have yet to own a copy of NM98.
@RockMyAmadeus is correct that the hoarding of NM98 far exceeded that of ASM 300 but there were a lot of people that were putting a few copies of that book away. I remember as a 12-13 year old buying a few copies thinking it would help pay for a car one day.
Remember that in the year prior to ASM 300, the Hobgoblin was unmasked, Peter Parker proposes and marries Mary Jane, Spider-man was shot and killed, and then this guy McFarlane came around. All of the issues leading up to 300 were must reads at the time. I remember as a kid being mesmerized by the art because it was the first time I saw something 'different'. I think it was the webbing that stood out the most for me. 300 was also a milestone issue and I think I bought a few copies NOT because of Venom but because it was a "100" issue which was still considered important. ASM 100 had been popular in the collecting circles and even in 1988, issue 200 was special (if I recall correctly) so why shouldn't I buy a few copies of 300.
Another edit... At the time Venom was cool to me but it was just another character. It wasn't the Hobgoblin. I don't think it was until about a little later in the series... by 316 with that crazy McFarlane cover of Venom that the character really started to spark my interest.