liquidity

Think of it like this:

If net selling price > original cost (likely situation):

Net selling price - Original Cost = taxed at capital gains rate
Original Cost - Book Value = accumlated depreciation = taxed at depreciation recapture rate

If net selling price < original cost (unlikely situtation):

No capital gains tax
If net selling price > book value, net selling price - book value = taxed at depreciation recapture rate
If net selling brice < book value, no taxes (you would actually get a tax credit of some sort)