Do dogs take the same medications that humans do for epilepsy? Isn't that very expensive?

Yes the meds are the same and from the same pharmacies. Phenobarbitol (Pb) is the first line of treatment, which is what is commonly used in humans, but if the seizures can't be controlled effectively, they add Potassium Bromide (KBr) to the mix. KBr used to be the sole medication for treatment of humans before Pb was discovered/created. KBr has a narrow range of effectiveness vs toxicity, so they don't use it in humans much if at all anymore.
Boomer is on both, and there are side effects, hind-quarter weakness and possible liver damage are the two main ones. The meds are about $80 for 3 months worth, vet bills were outrageous when it first set in, but he's worth it to me... Liver screens are required to make sure liver damage isn't occurring due to the Pb. that's a bit expensive, but are only once a year. I keep a journal and links (which are rather outdated at this point in time) of the ordeal. I am going to move my website and update it all someday.... BTW last seizure was last Thursday night, hopefully it's not until July for the next one, I would prefer never, but it beats the 4 week intervals we used to be on... (Sorry this is so off topic now)