Reputable sources? GSBs and Med Preps

So I am looking to pick up some Gillette silver blues (GSB) and Personna med preps. The prices on eBay are about half what the vendors are selling for.
Should I be worried about counterfeit blades? Are there other reputable sources for these that don't run close to $40 per 100 blades?
Thanks!

Robbins Instruments is the best for Personna Med Prep: $25/100
https://www.robbinsinstruments.com/colle...rep-blades

Razors Direct for GSB's: $20.99 shipped.
https://www.robbinsinstruments.com/colle...rep-blades

Yep, Robbins is where I get my Med Preps from too.

Robbins Instruments is the best for Personna Med Prep: $25/100
https://www.robbinsinstruments.com/colle...rep-blades

Razors Direct for GSB's: $20.99 shipped.
https://www.robbinsinstruments.com/colle...rep-blades

thank you! You are my hero
Any other secret places for blades that you guys know about?

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Good place for Gillette platinums http://www.polsilver-blades.com/gillette-platinum.html

Great lead EFD!