I start the year anticipating making about $40,000 profit for the year based on past history. By the end of 3rd quarter, I have a pretty good idea what my year end profit will be. This year it looks like it might be 2x that amount. That means I would have to pay taxes on that extra profit. Figure 25%fed and 9% state tax so essentially 1/3 of ANY profit above my estimate goes away to the taxman. 1/3 of $40,000 extra profit =$13,600 of additional tax that I would owe. Who wants to send an extra $14k off to the gubmnt?
So I bought a new Speedio. $100k, of which I can expense off all $80k of profit. That puts an extra $27,200 in my pocket this year. PLUS I get the extra $20k of section 179 next year which means if I can keep profit in the $60k range, I won't have to send more tax payments in than my current plan.
As far as tax brackets go, say the 25% tax bracket is 90-100k. All the income from 0 to 90 is taxed at the 15% bracket, and then ONLY the additional $10,000 would be taxed at the higher rate of say 25%. $90k x 15% = $13,500 taxes, PLUS 25%of the extra 10,000= $2500, so your total tax on $100k is 13,500+2500= $16,000 $16,000 is obviously only 16% of 100k, so really are not saving that much by just dropping you down a bracket.
Hope this clarifies a little, or at least doesn't confuse you even more.
Jon