For example if the chance of a collision (transaction) 9.7x10-29 how would that compare to say winning the lottery (US powerball)
Winning it 2 days in a row? Everyday for a week? Month? 700 years?
According to Wikipedia, probability of hitting the Jackpot in US powerball is 1 in 131,278,024. So the probability of you winning each and every day for more than 20 quintillion years (or 20 million trillion years) is roughly the same as finding a collision. That's about 1.5 billion times the age of our universe. If you win every second, you'll still have to win for 234 trillion years.
Flipping a coin and getting heads 1000 times in a row? or 100000 or flipping it every 10 seconds and getting heads for 6 months?
Getting heads constantly every second for a time interval that is about a trillion times the age of the universe.
EDIT: Corrected some remarks.
EDIT: These are completely wrong. I made a fool of myself, check out Holy-Fire's reply below. Guys, I have a maths degree, hush.