The 50% sale doesn't apply to the Crazy Domain Insane plan (L1), with or without a promo code.
The Code Monster (L3) is the one on sale at Sweet Dreams (L2) pricing--which is still more than L1, if that's all you need.
If you sign up for L3/Code Monster, you get to keep the 50% pricing when you renew.
If you're asking if you can do L1 for the first year with a promo code, which is barely over $20 for the year... then sign up for L3 at 50% off, then that would depend on whether they're still running the sale.
It seems like the sale has been going on forever, but if you're set on having L3 @ L2 pricing, I probably wouldn't wait a year.
I'd guess (but don't bank on my guess!) that the price is there to stay, but it probably gets more sales when you leave it as half-off, rather than just setting the price and dropping the L2 plan.
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