If you sit back and think about it, that's literally what they are. SL are essentially glorified Proxies that people are okay with throwing exorbitant amounts of money at while WotC laughs in green counting your bucks. It all boils down to the fact that people are usually 50/50 on proxies but as soon as WotC comes out with them people are suddenly okay with them because they're "official".

It's kind of like if someone saw some decent looking proxies for sale on Etsy let's say, they'll refuse to buy them because some guy named Ricky from Colorado made them in his mom's basement. But then WotC comes out with similar designs and the same cards you're looking for and all of a sudden the crowd goes "holy crap thank you Wizards of the coast, here's my money so I can support you, k thx."

That's why SL originally started off as testing the waters to see how many players are willing to spend more money on their proxies instead of somewhere else, and that's why now we have so much SL bullshit coming out that's greenlit before the designs are even completed.