Purchasing Tax Lien Certificates

[Austin Fisher]

Hi! I'm new to real estate investing/strategies, i have invested in REITs in the past, but never actually purchased real estate directly. I've did my best to do all my DD, but i did come up one answer short. 

I'm wanting to get into purchasing TLCs and to potentially get some in the county that i live in. The county doesn't do online auctions but have 1 sale of the year where they auction all their tax liens around November. 

However, they do have a big sheet of parcel #s and schedule codes, that are unsold tax liens, that from what i understand, are available for purchase.. but if they aren't auctioned, what determines the price of these properties?

Thanks in advance,