Do yourself a favor and skip this "deal" There are very safe booster seats out there for a fraction of the price. YES PLEASE keep your kids in boosters until they fit your vehicle's seats properly, but you do not have to spend this much for a good booster seat. (And I just bought a $500 car seat for my 2 year old, the Clek Foonf, so I do understand that all seats are not created equal and that sometimes it's worth it to spend more, but in this case, it isn't.)
At least one of those (two total...) 5 star reviews on Amazon is pretty fishy, as well, so please don't put too much credence in them.
Diono Monterey, <$120, fits kids to 120lbs (20lbs more than this one) and is well thought of by car seat technicians
Britax Parkway, <$105, also to 120lbs and well thought of
Graco Highback TurboBooster, <$50, to 100lbs, well thought of
Recaro Vivo, $80, to 100lbs
Recaro Pro Booster, $90, to 120lbs
And if you really want to spend a fortune on a booster seat, then the Clek Oobr is one of the best for $200, just a few bucks more than this one.
The ones I listed are tried and true, well known brands who are leaders in child safety seats in the US and other countries, and have MANY great reviews.
Sign me, an overzealous carseat nut, 5 kids, and I've owned close to 50 carseats for them, yes I am crazy! (And yes, my husband has given up trying to talk sense into me and just rolls his eyes when he sees UPS or FedEx bringing yet ANOTHER carseat!)