Estimating Rehab Costs - What am I doing wrong?

[Gregory Butterfield]

Hey there BP, you guys are looking handsome as always!

I am a hopeful real estate investor, attempting to use the BRRRR method, and I am having trouble calculating rehab costs. For example, while analyzing a property and taking notes on items that needed to be replaced; I had determined that I would need $18.5K in just materials. This was only to re-floor the house, rehab the 2 bathrooms, paint indoors, replace doors, and appliances. The $18.5K did not even include labor or any siding work that needed to be done to the property. I used the excel spreadsheet from The Book on Estimating Rehab Costs to make sure that I was including all of the materials that would be associated with these repairs.

After doing research I feel like $18.5K in just materials is way too high. While looking at one of David Greene's rehab projects in the same city (http://greeneincome.com/index.php/2016/12/01/alexon/), David paid $6.5K to have the property repainted, kitchen floor replaced, cabinets repainted, new doors installed, plumbing repaired, electrical upgraded, garage repaired, bathrooms refinished, new appliances and fridge installed, and some repairs made to a handrail. My estimate was way over that and I did not even plan on touching the electrical or plumbing systems for this project. With my rehab estimates always being at least $20K, I am pricing myself out of most properties and they don't seem to be in line with other investor's costs.

What am I missing BP? I did use Lowe's to price out the materials to at least get a ballpark so that may be part of the issue. Additionally, I tried to only pick mid to low grade materials and steered away from high-quality, expensive materials.
Any suggestions are greatly appreciated and if you would like to, please share some of your real-life rehab numbers on projects to help us noobs out! Thank you BP, you rock!