I was able to get them to honor the pricing.
Be polite and firm. Avoid using 'you' but rather refer to the company as "Amazon" in 3rd person (you can still refer to yourself in 1st person). Remind them of the 'relationship' you and Amazon share and how you are a loyal customer (I hope you are a prime subscriber)...
And with all customer service 'issues' be DIRECT in stating what you expect to be done, beating around the bush does no good. Directly say "I hope Amazon will honor the posted pricing" or something along those lines (but don't DEMAND anything, stamping your feet around throwing a tantrum like a child will get you no where).
I had good results in getting Amazon to honor the pricing with this strategy AND they threw in next day shipping without me asking for it.