For consumers wanting to buy "green," the choices these days appear endless. Unless, that is, you're on a budget.

Eco-friendly straws, sneakers, garments and packaging are often pricier than their conventional counterparts, leaving poor and middle-class people with not much of a choice, according to Bloomberg.

"There's a lot of innovation going on with sustainability right now, it's just not really affordable," Alexis Benveniste, who recently wrote about the phenomenon for Bloomberg, told CBS News. "It's hard to scale when you're paying more for a green product."

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For some products, such as organic food, the higher sticker price is reflective of the higher cost of creating that type of food. But others charge more simply because they can. "Eco-friendly" or "sustainable" branding is increasingly used as a marketing strategy to distinguish products as premium or elite, making them almost certain to appeal to wealthier shoppers.

Benveniste wrote, "It's no coincidence that it costs $20 to use reusable beeswax instead of plastic wrap to keep your food fresh, and you can even buy shoes that are completely made from recycled plastic—but they'll cost you $145 a pair."

Since the U.S. economy does not regularly impose a price on pollution, shopping in a "green" way is still a matter of consumer (or corporate) choice. That spells trouble in the long term, even in a world where most people are environmentally conscious. Shoppers do care about the environment, polls show--until they're forced to make a trade-off.

"[W[hen consumers are forced to make trade-offs between product attributes or helping the environment, the environment almost never wins," the MIT Sloan Management Review found recently.

That's why, for some companies, "green" marketing is more of a signaling strategy than anything else. Consider widespread plastic straw bans. This tactic, which Benveniste calls "a conversation piece," addresses just a fraction of one percent of the plastic waste humans dump into the planet each year.

If companies really wanted to make a dent in sustainability, "you'd think they would start with takeout containers, or other, bigger things," she said. "Straws are easier to scale… and they're not really a necessity."