Nope. To me, not even close to a $15K horse, but I have a higher level of expectation than many folks. I grew up riding horses that were worth much more than that. Dad turned down $25K for Buck, the horse I grew up on, but not only was he a totally bombproof beginner and kid safe horse, he was also a world champion performance horse and would put you in the perfect spot for a catch on either end of a roping steer every time.
As others have said, horses are only worth whatever someone is willing to pay for them and clearly they have found people willing to pay their prices or else their horses wouldn't be priced that high.
For myself, something that expensive, I expect a higher level of quality training on it. Sure, it's great to have a horse that is trustworthy, but those can be found for a lot less in today's market. A horse in that price range, IMHO, should not only pack around kids and beginners without batting an eye, but they should have the training and ability to step up their game and do a job well under an adult or experienced rider.
Also, that really peeves me that they advertise him as a "ranch" horse. I grew up on and around ranch horses and he's not one... not even close