Does it show what the premiums are without the subsidies? It's possible your income is placing you in a higher subsidized position than last year.
Premiums are based on the risk of the population in your zip code/county so it is also possible that it was a relatively low risk area and they overestimated costs last year.
Yes, the premiums without subsidies for a silver plan in 2017 is $656, 2018 $949. That's almost a 45% increase for 2018 if you're not getting subsidies but a
53% decrease if you're getting subsidies with a 32k income. That seems very lopsided.
I believe it was expected that unsubsidized plans would increase by 34% on average nationally but subsidized plans should not see an increase because the tax credits would offset any increase. I figured monthly premiums would stay about the same, not go down by 53%.
I'm definitely not complaining. I'll take the lower monthly premium and lower deductible but with all the media hype that 2018 ACA premiums would sky rocket, it's a shock to see the monthly subsidized premium go down by so much.