Technical distinction. Since mopeds require pedal starting and are generally < 50cc (and about 25mph max), I'm assuming you meant scooter. You've got a choice from most expensive to least; Italy (Vespa/Piaggio), Japan (the usual suspects), USA (Buddy). These are generally high build quality with prices to match.
The next group (and most popular) are the Taiwan or China bikes and there are too many brands to list. Most of these are clones of decades old air cooled Honda and Yamaha engines in either 50cc or 150cc. You can pick these up from $500-$1500 all day long and the quality varies dramatically depending on which factory manufactured the bike. You generally get what you pay for and it helps to be somewhat mechanically inclined.
Above 150cc, you get into the liquid cooled group and prices of $2000 on up. Again, China scoots are much cheaper (in all respects) than the others, but still a good value for the money.
They're all a blast around the neighborhood.
