The DotaLoot database has 95 items for Enigma, prices from $0.05. Rarities: Rare, Mythical, Immortal. Any of them can be won from DotaLoot cases or claimed for free in the daily giveaways — noticeably cheaper than buying on the market.
You can get Enigma items for free in the daily DotaLoot giveaways. The fastest way is opening cases — noticeably cheaper than buying on the market.
The cheapest Enigma item costs $0.05. Prices update based on the Steam market.