Basically, this seems kind of over the top, especially for a man who generally seemed against flair and fancy tomfoolery. Why does he talk so nonchalantly about buying a new Impala? Where is he even going to find such an old model car? Was dumping busted cars like this a common thing going back in Eazy’s era?
In 1987, a 1964 Impala was only 23 years old. For context, that's like a 1998 model car now.
While they're very valuable now, in the late 80s, a 1964 Impala was not nearly as uncommon or expensive. A presentable non-SS model could have been a few thousand dollars at the time. Good condition higher-end models might be closer to $10,000.
According to Hagerty, Chevrolet produced nearly 900,000 Impalas in 1964, of which over 500,000 were coupes (more desirable) and of those, 30,000 were the top of the line Super Sport, and around 50,000 were convertibles, both of which were particularly desirable in lowrider culture. So scarcity was not a big deal at that point in time, though ironically that same laissez-faire attitude towards preserving these common cars has led to them actually becoming very scarce and valuable in the present day, with good-condition SS models listed for $40-60,000, and pristine examples listed for six-figure amounts.
Given that this is Eazy-E, one can assume he's talking about a modified lowrider, with a few thousand dollars more in parts and paint. Due to the depreciation of parts after being installed, and the relatively low secondary market value of the labour that has been put into it, it is generally cheaper to buy an already finished custom car, than to rebuild one from scratch.