I would say that this is very cheap. 350 USD for functional Gold deck is nothing, if you are looking a bit into the future. Let's take General Sloan, 170 USD for level 6, that's 60 copies of that card, that's a lot. But once all those packs sell out and once land comes out I can see CL summoners sells 15-20 USD per BCX. That means your level 6 summoner will be worth at least 900 USD. Now that's expensive.
I know that 350 USD is a lot...it is a lot for me too but it unlocks so much for the future.
Don't get me wrong, staying in Silver is amazing, you will get really good rewards and that is a goal for most of the people but if you can stretch you money LIFE decks is least expensive way to go into the Gold.
I hope this helps :) Cheers!