There are mitigating factors, thankfully - the 68k architecture has always tended towards longer cycle-counts for instructions anyway, so even a fast CPU isn't always going to be running up against the memory bottleneck for every instruction (especially not math-heavy stuff.) And the 030 does include a little bit of high-speed cache memory (holds frequently-accessed instructions & data, and serves as a buffer between a fast CPU and slow memory.) Still, the 030's cache is small, and very few Amiga accelerators include any additional cache, so it only helps somewhat. (This is part of why an 040 can make such a big difference, it has much more cache memory.)
Chip ram is not cached and accessing slow custom chip registers wastes most of 040's potential. Depending on application more MHz is not helping at all. For CPU intensive applications 040 is better but sometimes 030 is more performant on Amiga.
When I upgraded my Blizzard IV 030 to BlizzardPPC with 040 disk performance downgraded (using internal IDE on A1200) but viewing JPEGs was much much faster.
