I bought around $2000 worth of packs so I feel your pain on the decreasing prices. IMO there are a number of reasons the prices are decreasing.

1. Our group of players have been spending with no cash rewards for a return for awhile now so we have spent our limit aside from picking up cheap cards.

2. People want that cheap Steem so sell their cards lower then their usual fiat value to get that Steem.

3. An abundance of free packs being given out hand over fist.

I believe we see an increase in price once the $100 daily / $1000 weekly tournaments come around. The sale was legit ... the seller meant to post it for $100. There was one that went for $155 directly afterwards. There are currently some below $200 still on the market as well.