I notice that Meyer's fertile eggs are not *much* more expensive than their chicks - couldn't look for details by breed as they are currently not taking orders til next month, but it seems to be something like a buck (apiece)more than the chicks.
FWIW there is a guy up here in Quebec who essentially runs a small hatchery, specializing in good strains of rare breeds, and he sells fertile eggs for about 30-50% of the price of his chicks i.e. the eggs are *less* expensive. His website says "We establish the price of eggs by holding account that the hatching rate is approximately 20% to 40% when the eggs are to dispatch by the postal service".
I am just guessing here, but I wonder if it doesn't boil down to the aggravation factor, so to speak. If your hatchery is all or mainly your own birds, it's less work to sell eggs than chicks so you might want to sell eggs cheaper apiece. OTOH if you are a big outfit getting chicks from 'subcontractors' it would be *more* (not less) complicated to sell eggs, since they will be in small numbers (inefficient) and require different handling.
Plus, no matter who you are, you are likely to have to deal with more disgruntled and whiny people with egg sales than with chick sales since so much of hatching success is totally out of the seller's hands (depends on postal handling and customer's incubating skills/luck). I would not blame 'em a bit for adding to the price to compensate for that or to discourage egg buying while leaving it as a *possibility* for those who seriously need/want it.
Just guessing,
Pat