They are only "overpriced" if the items offered are required for game play, they are not. Many players succeed without them. Yes, people can choose to take the easy path to success by spending currency. That is their choice.
Lowering the prices for non-diamond users would undercut the value the diamond users placed on their purchase of diamonds. Not a good business move for INNO. Additionally, the competitive balance would be shifted to making diamond acquisition a necessity, causing many players to withdraw from the game.
Some players have organized their play to acquire diamonds with minimal or no expenditure of currency.
You can spend currency directly in the diamond store for diamonds, Army Packs, Resource Packs, Building Packs, and occasionally various other items (FP, coins, Vic Towers, etc.).
The occasional offers for unique items, like the current Black Friday sale, provide an opportunity to quickly acquire items through the expenditure of diamonds offered at the price INNO feels appropriate to their business model, that is exactly what they should be doing.
I just would like INNO to offer more items using their current pricing schedule.