I don't know if pricing is similar across cities, but Amazon PrimeNow has Gillette Mach3 Turbo Men's Razor Blade Refills, 8 Count (Packaging May Vary), Mens Razors / Blades [amazon.com]
for $10.33 at my location.
Seems like a good price. Threw a couple packs in with an order I was already placing, but an order of 2 or more meets their delivery threshold.
I understand that not everyone subscribes to Amazon and that even fewer live in a PrimeNow delivery area. But please don't TD a deal solely because you aren't in the delivery area. Give folks that are a shot at seeing it.