When it comes to bathroom sinks, it seems like gunk builds up around the drain plug, rather than further down into the sink drain.
My current "fun." Wife and kids want a pool heater - we have a 24' above ground pool. We used a solar cover last year, which retains heat already in the water, but isn't the best about building heat. The water was a temperature we like by late July/early August, but it was a touch cooler all other times.
Cost of the pool heater - $2,300. We got 10% off with the pool store's anniversary sale, so about $2,000 plus tax, pushing it back up to $2,200.
Had a pool contractor give us an estimate to install the natural gas line and run it from the meter to the pool....a distance of 133 feet. Quote: $4,200. I'm sure it's almost all labor cost, but this is looking to be a $6,000 purchase.