Deductions & credits

Although I haven't seen a solid answer, in my opinion the threshold is based on the TOTAL amount (not just the business percentage).

 

The Regulation uses the phrases "property costing less" and "amount paid for the property".  To me, that means the threshold is based on the full cost, not just the business percentage.

 

https://www.law.cornell.edu/cfr/text/26/1.263(a)-1#f