The are fractionalized assets of the same types of commercial properties and sometimes larger residential properties. 

With NNN as total ownership or fractional as a TIC or DST it's all about the corporate tenant and the lease. 

Now I’m getting a masters in engineering for a fraction of the cost

The fraction is small and probably not measurable yet in terms of a city or a county.

Bank.I don't follow a budget, but my spending is a fraction of my income and I don't have an expensive lifestyle.It constantly amazes me at how many people claim to have no money while holding a drink from Starbucks. 

If debt on net balance is negative, how and why does the world have fractional reserve banking?

Comps need to be within a close area (and neighborhoods need to be known, sometimes close but across a certain street can be a huge deal value wise, mileage or fractional mileage for comps varies by population density) similar number of beds and baths, and square feet, as well as condition/upgraded status.

Sometimes there is a "royalty" or a fraction of the production that goes to the landowner.

When my contractor is done in a few weeks I will have a like new house for a fraction of its ARV.

Without the huge overhead costs of a large accounting firm, independent cost seg firms can get the same work done (often done better) at a fraction of the cost of the big accounting firms.