The price is fairly reasonable to be honest, at least in the context of what Sentai is charging to be the middleman. Whether or not you think JP prices for their home video market are reasonable is a different topic altogether.
If you order the exclusive edition from one of the JP stores, it will be 15,000 yen, which is $110 USD or £93. Considering Amazon is asking for 3600 yen on shipping for the regular edition ($26 USD or £22), there's zero chance that you'll be paying less than that for shipping plus proxy fees.
You'll also get the benefit of dealing with Sentai themselves if there's any damage.
By the way, the Amazon Japan price for the regular limited edition is closer to $106 or £89 when you factor in international shipping.