That is my actually cost. Looks the following explaination from another turbotax article does not limit the improvement to $2500.
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Improvements Election
This election is an option you can take each year that lets you write off some building improvements as expenses instead of assets.
Here are the rules you need to meet to take this election:
Your gross receipts, including all your other income, are $10,000,000 or less.
Your eligible building has an unadjusted basis of $1,000,000 or less.
The cost of all repairs, maintenance and improvements is less than or equal to the smallest of these limits:
2% of the unadjusted basis of your building or
$10,000
