I'd suggest it's because it's definitely going to be available here and being how they've previously been stung on MP Ghost Starscream TRU is probably shy of being stuck with 50% of their stock of an expensive item not selling. as such they are not selling internationally, avoiding undercutting their international counterparts.

that's my guess.

people that are spending upwards of $300 for MP soundwave on eBay today have more money than sense and don't deserve to keep their money. There will be store release of these in the states, and also here in Australia (as far as anyone knows) there is quite a mania going on about this at the moment.