So far I have bought the spare blades in 4-pack in the local retail trade. In a fit of boredom I looked on Amazon, but these things cost and behold:
4 pcs. To 9.90 compared to 13.30 at retail.
Even "naughty" is the pricing of the 8 pack (I nurnoch buy now) which comes to 17 away from Amazon, and retail up to 24 costs.
A comparison is worthwhile here as well, as with many other personal and home care products (ever watched the detergent prices? !!!!) And a purchase of stocks will help here to save you money compared to the impulse buying!
Who pays more, is your own fault!