Replace rim because of 4 broken spokes? When replacing the rear brake pads I noticed that 4 spokes were broken and the wheel wobbles.  I phoned a local bike shop and was told that they recommend replacing the wheel if more than 3 spokes are broken.

I assume that this is a safety precaution but wonder if the recommendation is in line with common practice.  I certainly have no desire to get thrown off the bike in traffic, but it also seems a waste to (probably) discard an entire wheel because it might be damaged and might fail at some point.

This is a 27" road bike, inexpensive, which I ride for transportation in the city (Tokyo).

The rear rim is a bit scored from waiting too long to replace the brake pad, which is another factor to consider.

To clarify slightly, it probably would be cheaper to replace the wheel as suggested below.  My objection is more of an ethical one -- tossing something useful into a hole in the ground seems irresponsible.  Difficult to avoid though, the way things work right now.
On a reasonably built and loaded bike (which is how I hear you describing your bike) with well built wheels I would expect the wheels to last a very long time. With that in mind, several broken spokes with no obvious cause are a red flag. My first thought would be inadequate tension leading to flexing and fatigue. If that is the case, other spokes will likely follow.

With a damaged rim, it might be worth biting the bullet and buying a new wheel – or if you have a good hub, having it rebuilt.

If you're inclined to do the work yourself, replacing spokes isn't too hard and the tools are reasonably inexpensive. There is a knack to truing wheels, but you'll be starting from a reasonable place and all you will likely need to do is to tension the new spokes.