That sounds reasonable Kevin but does it hold up in real life? Comparison of apples and apples is hard but in general I believe you will pay something extra for going faster. Most buyers find the extra cost worthwhile, the "it's the destination" crowd, vs the "it's the journey" people who appreciate the lower cost per hour under way.
To compare the Dyer 29 above with a current model Chris Craft 28' Launch. I'll use the CC only because I found they have some excellent performance data sheets on their website, well done CC.
The Dyer is 26' on the waterline, weighs approximately 6700 pounds, and has 160 installed HP.
The CC launch is 23' on the waterline, weights (test) 8300 pounds, and has 440 installed HP.
At 10.9 knots the Dyer gets 4.04 Nmpg.
At 23.24 knots the CC gets 2.65 Nmpg
So for a 25 mile trip the Dyer burns 6.18 usg while the CC burns 9.43 usg, we currently pay about $1.30 per liter so cost for the Dyer is $30.42 vs the CC at $46.40.
Some of this difference is in the hull forms being optimized for particular speed regimes, but not all of it. Travel time saved will cost something. The Dyer and the Chris Craft have similar amenities, taking less with you is another way to save fuel while increasing speed. Longer, lighter hulls are a possibility, but moorage logistics generally rule that out.