well, there are plenty of people who are willing to make a big capital investment and have a "grow room" of their own, lots and lots of them are medicinal patients with proper papers for their medication
30 plants @ 1-2 oz per plant aint much... plus sometimes plants die, sometimes u r testing them, and sometimes certain plants wont give u a big yield per capita

1 lb is 16 oz and a daily smoker can go thru an ounce in about 5-7 days moderately and smoking alone

so u see... if u r like many other people a "smoker" not just a casual toker... you would do the calculation (other than risk factor) and see that u save shit load of money when u get a customized home grown herb plus it turns into kind of a hubby cuz it needs time and attention so it fills up your time as well

If i was gonna grow for me, i would gauge my consumption in 1 week and then based on that and the strain of plant i like... i would grow enough plants to cover me until before my 2nd round harvest.. meaning what i harvest @ 1st round should last me all the way thru few months until i can get my own next harvest

1 more hint: most commercial grow areas are not too neat n clean... some are top notch, but most show signs that they are commercial and not personal
like having far more than 30 plants! or being in larger rooms with thousands of dollars worth of equipment... not like a few hundred bux! or u will see many custom made systems for plants, like many dirty looking buckets and hoses and wires running all over the place... cuz they are business, they only work on the money maker part, forget the look of the area, as long as germs dont kill the harvest! or sometimes u see a whole house including the restrooms used as well,

just google some grow bust, DEA is more than willing to post up pictures of the gardens for most of their major operations

most commercial grow busts net hundreds of thousands (sometimes millions) of dollars worth of weed in street price and thousands of dollars worth of equipment! say $6000 a pound sale price and needing min of 8-10 plants to get a pound, only in a $50000 bust, u will have to have grown 80-100 full blown plants