First, have the item at it's normal daily rate.
Then, create a package. (Learn More) Creating a package for this item allows you to have a different price while still tracking the individual chair. You should not create a second inventory product with a different price - this will "double" the number of chairs you have.
Next, add in the discounted rate for that item in the package's pricing.
After, in 'Contents' add the item you want to discount to this package.
Finally, on your projects add the 'Chair Holiday Deal' and you'll add the item at a discounted rate!