Exactly, this is what I don't buy in the "black market will get extremely unattractive" argument. The status quo is to buy illegally (but with very low risk for the buyer, and usually excellent anonymity) from established dealers, often people with a lot of knowledge in growing/processing. The new legal approach would be to either grow yourself, or join a club [0]. I don't consume cannabis, but if I would have to choose between joining a state-registered alcohol club, brewing my own beer, growing my own grapes, or just buying a bottle of wine illegally now and then from someone who has expertise in making it (and with nearly all risk on the seller side), I would definitely opt for the latter.
[0] https://en.wikipedia.org/wiki/Cannabis_Social_Club