From "plant design and economics for chemical engineers" by S. Peters:
The capital investment for engineering and supervision (design,engineering,drafting,purchasing,accounting,cost engineering,...)is approximately 30% of the purchased equipment cost or 8% of total direct costs of the plant with the following break down:
engineering 2.2%
drafting 4.8%
purchasing 0.3%
accounting,construction and cost engineering 0.3%
travel&living 0.3%
reproduction&communication 0.2%
TOTAL 8.1%
hope to be helpful.