This thread has been kind of educational to me. I never buy private party because I'm usually looking for a young horse or broodmare, not started. Because I show and breed, I'm very picky about registration and bloodlines, of course temperament and conformation too. I tend to find the horses I want at people's production sales or a dispersal sale and they go for what the highest bidder offers, unless the reserve isn't met.
I've always felt that a beginner or beginner's father or husband who squeaked at spending $5K or less for a well trained horse, reg'd or not, really didn't think their loved one's life was worth much. To me, $5K or less is a very cheap life insurance policy. Yes, you can buy a horse for $1500 or less, but if he's not been well trained or used in a lesson or trail riding program then you can't be sure he's a Steady Eddy.
This horse, while not dirt cheap, isn't hugely expensive either. He's been well trained, is in comfortable middle age and you've ridden him long enough to know there's no "side" to him. He's also packed around other riders and is used to different riding styles, so he's not going to be inclined to be fussy with your or another beginner. You're comfortable with him and you trust him, that's not to be taken lightly. I've had 2 horses that I trusted implicitly; Lucky that I had all his life and Marq, whom I bought by accident at an auction and I trained him and sold him for a LOT more than $3700 and I'm still kicking myself for selling him. If this horse even comes close to being able to be trusted like I trusted those 2, I'm not kidding when I say priceless.