Where can I buy cheap dumbbells? 60lb pair

What country? Around here, which is in the US, Big 5 can be cheap. Check advertisements for yard sales.

In Washington DC, on Capitol Hill

I agree re yard sales - they are usually full of exercise equipment that's barely been used. Or try eBay or Craigslist.

Pawn shops

In my neighbourhood you wouldn't bother buying dumbbells. They'll be out on the sidewalk the night before garbage pick-up. One of my former neighbours got all her workout gear that way.

I helped her drag steppers and treadmills home. She had her son pick up weights using his truck.

Thus proving it's much more fun to buy exercise equipment than to use it.