Yea, that's top money but all things considered it might be worth it to you. Say, if it's super excellent and totally loaded with has some sort of pedigree like an ownership history with records/receipts and a clean damage history (...don't rely on CARFAX too completely, actually inspect it yourself or have someone inspect it for you).
Is it from a dealer with a solid reputation? Is some kind of warranty included? These things can inflate the price. Is the dealer the type targeting low to no credit customers? That increases the price too, sometimes by thousands. Thousands in the asking price and thousands in additional interest down the road. They're pretty much non-negotiable too.
At the end of the day, with lots of research and work, you should be able to find the truck you want in the condition you want with the mileage you want in your price range. It just takes legwork. I shoot for totally loaded top-of-the-line models at the lowest trim prices.
On pricing - you can run through all the research KBB, NADA, etc and get an idea of what they're selling for but if you REALLY want to know then you've got to call the ones out there for sale, eBay, craigs, autotrader, your local paper, etc. and find the sold ones. Get that price. That's what they're selling for. (completed eBAy auctions is a start). There's nothing wrong with KBB and NADA but they largely get their prices from auctions (Manheim) and adjust their prices up. Depending on seasonality, region, and all kinds of other reasons prices typically get adjusted up anywhere from one to two thousand dollars (which is the typical dealer markup) but even still that's not all that accurate. You've got insurance companies (allegedly) and all kinds of other factors influencing the prices too.
I think of it like this, if you can get what you're looking for, for anywhere from one to two thousand less than the lowest trim level on KBB or NADA you're probably doing ok.
...former wholesale auto industry analyst here.
Also, that's not the only dealership or Tahoe in town is it? Go somewhere else - don't be so magnetically attracted to get that one down.