OPINION!
Some of the newer dry beer yeasts are expensive, but the ones that have been around for a while are quite cheap. S-05, S-04, Windsor, Etc are all around 1.99 to 2.99 a sachet of 11 grams of yeast. Aren't wine yeasts usually sold in 5.5 gram or 6 gram sachets? So, double the amount of beer yeast than wine yeast?
I think the newer dry yeasts are more expensive because of R&D, marketing etc to get a new product to market.
One thing we don't typically see has home brewers is the wholesale price of the yeast. I have 3 home brew stores within a 30 mile radius of my home and their price on yeasts and hops varies quite a bit, but their price on grain, extract are quite similar. I think for a home brew store trying to increase their margin it is easy to do on hops and dry yeast, raise the price $1 (33% increase in price, 50% increase in margin) and it really doesn't make the beer that much more expensive to brew and doesn't deter a customer. I'm not going to go to a homebrew store further away or that Im not familiar with, or mail order a sachet of yeast to save $1.50 on a $50 ingredient bill. I'm just gonna pick it up and buy it and say oh well.