LOL.
Prices vary from one MA to another because all the shops are part of a franchise! Different people own different shops/different groups of shops so personal opinions will come into play there...
But generally there is a lot of things that affect the prices between shops, bigger shops can buy livestock in higher quantity and more regularly and so can often haggle to get better prices on a lot of stock, espeially things like Zebra Plecs that are bred by various staff members.
Then there is also the location of the shop, shops in more afluent areas will have slightly higher prices than those in less afluent areas/small shops in villages etc...
And also the local competition, you dont want really low prices compared to local shops (this does sound backwards!!) but being cheaper isnt always better, it means you just make less money.... likewise, there is no point being way over priced compared to local competition unless it really is of far better quality.
A lot of thought does go into the prices and deals.....
And there is also the fact that there are about 120 odd shops and every week/two weeks we get lists with 20 odd suppliers for fish from different countries. Each shop can pick and choose what fish they get from where, fish prices change every week and so does the rate of exchange often. So fish from Europe will always be a LOT more expensive than fish from places like Singapore that has a better exchange rate... but not always best quality fish... South America has a poor exchange rate and declining species lists.... so fish will be more expensive....
You also pay more to have a box with 10 species in lower numbers than you do for a box with 4 species in higher numbers (packaging costs and so on)...
Just a few things that affect price...