This gets complicated quickly, since price/pound is a poor measure of how it works out in the end.
Epoxy is about 5% lighter by volume than polyester
Epoxy also allows a properly designed structure to eliminate 10-15% of the volume of laminate because it is so much stronger.
Put together this means you could very well end up using substantially less epoxy by volume compared to a polyester boat! but at a substantial price
increase for the hull
. But you save substantially in the weight department as well.
The fun part is that by reducing weight you can further reduce the structual elements because there is less mass to worry about, and momentum is reduced because of the reduced weight...
Basically it becomes a beneficial spiral that all works to reduce boat weight, and forces incurred. But at a cost premium.
How much the premium is really depends on the design, and the redesign (to take advantage of the better materials), and how much of the total boat weight is concentrated in the structure. A stripped down racer
will notice a much higher weight reduction by percentage than a long distance cruiser.
Then there are other issues...
Epoxy and vinyl construction don't require a barrier coat since they are naturally water
impregnable. Which can save substantially over the life of the boat.
Gel coat doesn't stick to epoxy (tho epoxy will stick to gel coat) which raises issues with repairs
down the road.
Frankly this is a huge issue, and if there was a clear winner the other two would disappear from the market. My preference is for epoxy boats, but there is a limited number out there.