If the tubes are too damaged after a reversal it's extremely difficult to conceive. ivf isn't guaranteed to work, but neither is a reversal. As Clysta said, the odds of ectopic pregnancies after a reversal is pretty high. Reversals here cost from $8,000-$12000 so they're definitely costly.
It's possible if you opted for a reversal as well that you wouldn't even qualify. It depends on the damage to the tubes, the type of ligation performed (there's half a dozen ways to do it) and the skill of the doctor. The average reversal is around $5,000, IVF is around $10-$15,000 and not all of these are covered by insurance.
IVF, but it's just as expensive as a tubal reversal, if it doesn't work you have to continue doing it until one sticks with you! You are better off with a reversal, you can try on your own, unlimited tries. It is expensive, either way. And you aren't guarenteed to get pregnant after a tubal reversal (not that even without a tubal reversal you're guarenteed). I have a girl I worked with that got her tubes reversed 2 years ago and is still not pregnant. So make sure you don't smoke drink, and are in good physical health to get pregnant, eating healthy, and you'll increase your chances!! Good luck hun!!
Less than 1% Unless you do adoption, IVF or a reversal your odds are extremely low, and even if it did happen is more likely to be Ectopic. This is because a ligation is meant to be permenant and not fail. If you wanted more why were you sterilized?