Boss Laser resells cheap Chinese machines similar to the ones on eBay with a hefty markup. Don't expect major differences between the two. However, keep in mind that buying from eBay means you'll have to support the mache yourself. It is not difficult. These machines are made with standard off-the-shelf components.
I wouldn't recommend the eBay machines for serious production, but for a hobby, they are just fine. If you want a quality machine for cutting, later on, I would suggest contacting GCC and asking them for a machine with a "glass tube". In my opinion, currently, they are the best option in terms of price-quality. They also have a local rep. and repair/support center in the US. A 100W machine should be around 8-9K.