Short answer:

1 sous per egg isn't a bad ballpark estimate -but-- prices varied significantly, and egg prices mattered much less than grain and bread prices. A 4 lb loaf of bread was 9 sous in 1788, but 14 sous by 1789. A laborer might earn 25 sous per day, a skilled artisan might earn 100 sous per day in 1789.

Discussion

There's a _lot_ of economic history for 18th century France, and agricultural prices varied quite a bit. First by way of preface, eggs are a somewhat unusual commodity in that quite often the eggs consumed were produced by the household. In observing "market prices for eggs", you're looking at something that would less commonly have been bought; wheat is a more reliable indicator of a consistent agricultural market, in that if you weren't yourself a wheat farmer, you didn't have any endogenous production.

George Rudé has a fine piece that summarizes a lot of data and sources, and one of the more interesting are the data assembled by the notorious Committee of Public Safety, who in addition to the more sanguinary feats for which they're better known also did a lot of gathering of economic data. They conducted detailed research into prices through the nation from 1790 to 1793, and while 1790 is technically during the Revolution rather in the "lead up", its before much of the economic chaos and the great inflation that hits later on, especially from 1793-95

Rudé has figure from the Committee of 4 livres, 4 sous per hundred eggs in June 1790; (there were 20 sous in a livre). So that's 84 sous per 100 eggs, a little less that 1 sous per; a reasonable number to work with but within a few years or in other places it could have been double that or half that. This is consistent with figures from d'Avenal from a little later.

What makes all this complex is that France had poor harvests and rising prices immediately prior to the revolution -- we often think of a food price inflation during the Revolution, but of course there were massive shortages and high prices before the Revolution too, that's one of the causes of popular discontent. So when looking at prices at the beginning of, or in "the lead up to" the Revolution, you're looking at prices that are higher than usual.

So if you're looking for some "undisturbed" or "normal" price for agricultural commodities, you'll have to push back further into the 18th century, and even then it varies considerably from year to year, and from place to place; we are used to a great deal of stability in agricultural prices, but that wasn't the world of the 18th century. France had famines quite often during the ancien regime - notably in 1693/94 and 1709/10. One scholar, Marcel Lachiver, has estimated the deaths due to famine in 1694 at 1.3 million people; the question at such a time wouldn't be "what was the price of eggs" it would be "has anyone seen any food at any price"

There is a nice article by Martin Bruegel and colleagues detailing the food purchases of a wealthy convent school from 1703-1788, using their account books, but Bruegel notes that the convent was producing a lot of their own eggs. Looking at the books of this wealthy convent, one where people ate very well, Bruegel notes

The forms different food expense indices took in the course of the century bolster the assertion that the rising taste for sweets and the corollary requirement of butter and eggs necessary to its gratification combined to bring down expenses for butchery meats

. . . in other words, during the 18th century French culinary tastes -- among those wealthy enough to vary their diet-- were reducing meats and increasing butter and eggs. Such a shift probably didn't happen with folks poorer than the daughters of the wealthy at Saint-Cyr, whose diet Bruegel summarizes

Cornucopia notwithstanding, the diet at Saint-Cyr displayed unexpected features. Bread furnished about 60% of the available calories. [my emphasis] Butchery meat, the other staple, provided 25% on average. However, it varied surprisingly. Its contribution rose first, then declined, only to rise again. The presence of these heavyweights limited the caloric contributions of other products. Eggs and butter remained essentially stable over the century. Milk's contribution grew, an increase whose effect on the health of the demoiselles warrants further exploration. The importance of meat marked Saint-Cyr's diet as aristocratic. The reduced place of dairy products - the total amount grew from 5% of calorie availability at the dawn of the century to 9% during its last decade - was in line with the lactose-poor diets at other French boarding schools but distinguished Saint-Cyr's fare from the rations distributed in the Amsterdam Burgerweeshuis where orphans received 25% of their calories from milk, butter and cheese (meat provided 7.5%)

Note the enormous percentage of calories that derive from bread! Bread was how the ancien regime filled the bellies of both the rich (less so) and the poor (moreso). Bread prices, far more than egg or meat prices, would have been the "gas prices" of the day, the price that everyone paid, everyone noticed, that enraged and was remembered. As Bruegel notes, these dietary habits varied significantly from place to place-- in the nearby Netherlands people were eating much more dairy, and one suspects the same would be true of eggs that there was substantial regional variation.

Sources

Gráda, Cormac Ó., and Jean-Michel Chevet. “Famine and Market in Ancien Régime France.” The Journal of Economic History, vol. 62, no. 3, 2002, pp. 706–733

Galloway, Patrick R. “Differentials in Demographic Responses to Annual Price Variations in Pre-Revolutionary France: A Comparison of Rich and Poor Areas in Rouen, 1681 to 1787.” European Journal of Population / Revue Européenne De Démographie, vol. 2, no. 3/4, 1987, pp. 269–305.

Rudé, George E. “Prices, Wages and Popular Movements in Paris during the French Revolution.” The Economic History Review, vol. 6, no. 3, 1954, pp. 246–267.

Lachiver, Marcel. Les années de misére in "La famine au temps du Grand Roi". Paris:1991

Bruegel, Martin, et al. “Explaining the Food Purchases of the Convent School at Saint-Cyr, 1703-1788.” Annals of Economics and Statistics, no. 109/110, 2013, pp. 63–91