For better or worse, people, on average, value the lives of animals far less than they value the lives of humans. So we have to limit the scope of drugs to encompass only drugs that are available to both humans and animals.

Here's 500mg Cipro for animals and 500mg Cipro for humans. 35¢ vs. 39¢. I think that's probably pretty close.

Fluoxetine (Prozac): veterinary 30¢, medical 57¢. That's a sizable difference.

Lysodren: veterinary $9.99, medical $4.87. Also a sizable difference, now in the other direction.

Selegiline: veterinary $2.50, medical $1.70. Still leaning the wrong way.

Tapazole: veterinary $1.79, medical 87¢ (or 33¢ for the generic). Your argument's not starting to look so good.

For the record, I went through this page and picked the ones that seemed likely to have a human analog (I guessed wrong a lot) and appeared to maybe be non-generic (except for the fluoxetine and cipro). I don't think I cherry-picked any data. Honestly, I was surprised. I thought you would be more right; I thought I was just going to show that the differences weren't all that significant. I recognize that this is largely anecdotal, given my non-scientific data set selection. If you have other better data, I'd be glad to see it.