My mother was a farmer's daughter and I've been happily surrounded by animals my entire life. I've spent over $3,000 for a dog and I once flew from NY to CA to buy a kitten for $2,500. Having confessed to my sins, let me say this...
My rationale is quite simple. If I buy a dog for $3,000 and he lives 10 years, s/he only cost me $300 a year. That's less that $1 a day. I can assure you that every one of my babies is worth much, much more that $1 a day.
Beyond that, just make one trip to the veterinarian, take a look at the bill, and you will very quickly forget about how much you paid for your pet.
My bottom line is, if you can afford it, enjoy it.