That's how they are available in the shops in CA, OR & WA that I know of. Was surprised myself to see Shanti offering them in 5 & 10 packs. Dunno what the markup is, but at the clubs I worked with they were ~$100/pack.
Packaging is legit, seeds look fully mature, good luck with em Rob
I'm just finishing up my first exp with mango haze (inbred, though), & I'd advise flowering small clones as opposed to seedplants if you are running inside and/or have a harvest deadline, lol. My seedplants got huge & some wanted ~4months to flower.
EDIT - Yo Rob, just saw in your post that you are kinda new. If you are running these outside (late feb, got em at a dispo...), Id really advise taking clones from your seedplants & initiating flowering on them. The ones that will trigger relatively quickly under artificial 12/12 lighting are the ones that will finish before halloween. The ones that get huge on the 12/12 flip will run thru Nov. I was @41 deg in the sierra foothills & really wanted to pull by ~oct 20-25 at the latest due to the oncoming badweather. Even in a GH, those coastal storms will blow the house down, lol.