This is a very typical price. I have seen pairs of "common" apistos typically priced between 25 and 50 dollars a pair. I once paid a retail shop $75 for a hot new species. On the other hand it is still possible to find tanks of wild imports for $7 or $8 per fish. However, most pet stores won't order them because they can't sell them.
I consider $28 for a known pair to be a great deal for these reasons.
1. When I mail order order fish I have to pay shipping which can be incredibly expensive. I recently sent a small box - 3 pounds across country overnight and the freight was over $100! There were four pairs of fish in the box so these were $25 a pair just for shipping. Of course there are cheaper shipping options and priority mail can be very inexpensive but the longer delivery time can cause trouble. Additionally there are a lot of inconveniences that can arise with ordering fish like DOAs, arranging schedules, making sure someone can accept delivery, etc..
2. The Pet store needs to make a profit. When a shop buys apistos as pairs or in small lots they do not get good discounts and the fish do not come to them cheap. Then they have to pay shipping and offset losses. Next they have to keep the fish until someone buys them. Unfortunately for the shops, they often end up with a few less desirable fish that they never sell. All of this has to be accounted for in the price they charge. Then there is the cost of paying a staff person to catch and bag, etc. When it comes right down to it the shop is probably only making a few dollars on the sale.
3. Apistos are expensive in shops because so few people buy them. I referenced some of the reasons low sales cost the shops above but the bigger issue is that with few shop sales there is little demand to the wholesalers. When they have little demand they don't create demand among breeders. Without a lot of breeders there is not a lot of supply and the prices stay high. It would not be difficult to set up Apistogramma hatcheries that could turn out large numbers of healthy high quality fish but there is not enough demand to keep the hatchery in business. Thus not as much supply.
4. Hobbyists in other countries are willing to pay higher prices. This is a fact and a primary reason that so many of the most spectacular species are only seen in the US in photos. It is not unusual for a quality pair to fetch hundreds of dollars in some Asian countries. Even with the more common species the prices they pay are higher than what we do. Thus, the prices rise significantly.
5. The most important reason I consider $28.00 to be a bargain is that the shop actually had them! I have visited hundreds of shops around the country over the years looking for dwarf cichlids and have found them in very few stores. As the chain stores continue to displace the independents I expect to see even fewer in the future. If I want to be able to find dwarfs in shops I have to be willing to buy them when I find them. I don't think that I should expect to not only find them but to get a great price on them to boot. Sometime that happens but not often. My bottom line is that I have to be willing to support the shops that make the effort to bring in the fish.
I'll get off my soap box now but, as you can tell, I am passionate about this topic. BTW- I do not and have never worked in any type of retail pet store and I breed and sell dwarf cichlids through mail order.
DC