Are these watts right?

What was your normalized power, and how much do you weigh?

247 watts for 50 minutes steady...no warm up or cool down is likely inflated power if you don't consider yourself a fast biker.  Generally people that can just hop on the trainer and do that type of wattage at a moderate effort are very much FOP on the bike at triathlons.  

It's difficult to translate to speed since all courses are different, but if that power were accurate, I would suspect you wouldn't be outside the top 15 overall on the bike at a typical local race with 200 people.  Possibly even top 5 if your position is good. 

Was rider size put in on the Kickr? What type of course was ridden on it? I don't know what all it does or takes into account, but hadn't seen those asked yet. Something doesn't seem to be matching up, so start with the setup. Make sure everything you were supposed to enter was, and was done correctly. Then you can start taking the course into account.

That's a pretty impressive number.  Those numbers aren't too far from my FTP and weight (260 and 155), and I'm a 24ish mph guy on most local courses.

Your not the only one!  Seems like there's a lot of variability in units out there.  Not great for something of this expense.

Sounds a bit high, but honestly, if you're averaging 22mph on race day outdoors, you will be pretty close to 250FTP at your weight. 

I would say you're leaving some speed on the table if you're averaging 22mph off 250W.

Did you do the spindown calibration once the unit was warmed up?  When I first got my KICKR the watts read about 10% high compared to my Quarq.  I had never done a spindown with it.  Once I did the spindown calibration it was only a couple of percent off.

Without another power meter that you trust you will never know, but there does seem to be an issue with some kickrs both drifting throughout a workout and reading high, even after spin down and calibration with their own calibration kit. Between the ST thread referenced above and the other ST thread about "controlling the kickr with another power meter" it seems that many have come to believe this is an issue with some newer kickrs. FWIW I got mine when they first came out and it reads well within the combined margin of accuracy with both my vectors and quarq. It does drift a bit as it warms up, but a spin down fixes that (actually I keep it plugged in and don't do a spin down anymore - it just gets more in line with my other power meters after about 20 minutes of warming up).

Just to give you another data point I rode 24mph at nationals on 213w at 148lbs, and with what I believe to be a pretty good position. That course is about as flat as they come, and the wind was light, so overall a pretty good indicator of speed/weight/watts.

How are you determining that your FTP is 258?  ehat was your testing protocol and the results?

Maybe your Kickr is still reading high, but if its consistent with the spindown then that's what is important and just use the numbers it provides you.