It's not a matter of Vanguard "honoring" the 5% discount. Vanguard didn't promise a discount, ETP offered the discount.
Vanguard has to enroll your shares in the ETP discount drip program with ETP's drip administrator for you to get the 5% discount.
From the price you paid, it's obvious Vanguard went to the market and bought your drip shares. They paid whatever the market price was at the time of their buy.
You can ask Vanguard to enroll your shares in the discount drip, as some Schwabbers have done successfully. If Vanguard refuses, you can simply move your ETP shares to another broker, like Fidelity or Ameritrade, which does participate in the discount drip without being asked.
If you are angry enough, you can move all of your accounts from Vanguard, letting them know why.
If your accounts are big enough, you can threaten to leave if they do not give you the drip price or some other financial equivalent.
I once ordered 9,000 shares of an IPO and Fidelity gave me 122. I went absolutely ballistic with rage. Fidelity knew they were going to lose all my accounts over this. Not only did they buy my puny 122 shares at a profit, they gave me 100 free trades.
dar200 I finialy receive call from vanguard re: DRIP of ETP,I told Vanguard last week that they costing me money and I would think they wpuld surly be looking out for my best interest and that I would move my EPD and ETP to Fidelity if they do not offer the 5% disc. To day they called and said they are looking into it and if Attys agree they will handle it for me. They said will take 2 maybe 3 weeks .3 weeks seem long but I will give them 3 weeks if not I am going to Fidelity with 14m shares