Oh my, you and Archer have been through a lot. I am sorry to hear of Archer having troubles. I hope he gets back on track and starts feeling better soon.
CVS and Walgreens both take GoodRx coupons, but prices do vary depending where you are. A 90 day supply of generic Keppra where I am at CVS is over $300 WITH goodrx and $181 at Walgreens with goodrx and the pharmacies are within 5 miles of each other, some right next door on the next block.
Perhaps, try this: Google "pet prescription discount cards" for other options, and you could ask CVS or Walgreens if they take cards like this one: http://iheartdogs.com/pet-rx-discount-cards/
I use CVS too and if I ask them to see if they can find it cheaper using other discount pet cards, they plug in some without me even having a card.
Did you try Diamondback Drugs?
DiamondbackDrugs- your vet can call them with a script, then DD calls you for payment. I usually receive orders within 3 days paying the $8 shipping, and I am on the east coast. They ship from west USA, I think Nevada. They will also give quote to either you or vet. However, I do not know what pharmaceuticals they have for the generic brand. http://www.diamondbackdrugs.com/
Allivet.com has the generic - Levetiracetam - in 250mg up to 1000mg for $.23-$.64 per pill (depending on type: they list oral solution, then regular tablet, then the XR which is the extended release form) and some mg's cost less if you have to get 100 or more. Your vet can call in the prescription for you. I just don't know what pharmaceutical they have, but I am sure if you call them, they will have an answer. Here is this prices for it and it's free shipping for order over $49:http://www.allivet.com/search.aspx?Sear ... etiracetam
I have used both Diamondback and Allivet for my Buttercup.
I hope Archer is better soon. Be sure to take care of you too.