The problem is that you want high quality for a low price. So that leaves you only with one option...the used market. Craigslist, OfferUp, Letgo, etc. More on reddit.com

Looks like you threw some cushions on a stack of pallets.

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Please report back in 6 months and let us know how it went. More on reddit.com

I would avoid using the green type of treated lumber at all costs. It is called borate plate material, and toxic and ugly. technically, the green borate material is only supposed to be used indoors in contact with concrete. the outdoor treated product is called copper azole. it is treated with a different chemical/process. this is the type of treated lumber that is meant to be used outdoors (decks, steps, patios, etc). I dont like treated lumber because of the indentation pattern left in the wood during the treatment process. it has a very utilitarian appearance. I would use cedar, it can be expensive, but you can find good deals if you go to fencing wholesalers and dig through their piles for the best boards. also, teak, white oak, and even red oak if finished properly will last for decades outdoors. EDIT: you can try to stain it dark, but with any direct exposure to the sun, the darkness will fade rapidly. as far as the type of final coat, it depends if you want a glossy hard coat finish, or just a natural wood look, with the intention of the wood being protected from rot, but allowing it to "age" naturally. If you want a good hard glossy finish, i would use a spar varnish. this stuff rocks. if you would prefer a natural look, try a penotrating oil finish. there is a company called Penofin that makes a great oil finish that protects the wood from bacteria and moisture infiltration. remember that the objective is to keep lumber free of moisture, because it is moisture present in the depth of the wood that encourages bacteria growth. nothing will stop the effects of the sun, but a well protected board will last a long time, only turning grey with prolonged exposure to uv rays. the reason some woods ie cedar and redwood perform so well outdoors is because they have natural oils that protect the wood from moisture and bacteria/bugs. More on reddit.com