My take on this is that I am a hobby cheese maker. I don't really have to worry about the bottom line.....for me, a great result is worth a few extra pennies or dollars. I am totally sold on making a mother culture. I brewed beer for years and made many pitching cultures which is the way to go since it removes the chances of contamination since the yeast (in the case of beer) has a firm foothold and can outcompete any "invaders".
I have a number of easily sterilized containers that I can put a 1 to 2 percent amount of desired culture in and make it according to Sailor's instructions. Works a champ so far. I like it much much better than just tossing in some dvi powder and hoping. I'm still having pH meter difficulties so I'm not sure if things are working perfectly but the results are pretty good. I'm going to buy a Hanna 99161 since my ExStick 100 (and 110) seem to have issues. I know a lot of people have had no issues but I'm on my fourth meter and it still measures all fresh milk at 6.9 or above....(and yes, I know how to calibrate it and I have made sure i have fresh and reliable calibration solutions.)
To be frank, the timing has been working for me and I am positive the mother cultures are a huge benefit. My procedure is to take one of my sterilized containers, they are about 8 oz, and fill 90% with skim milk. I heat to 200 degrees and hold for 30 min. Then I cool in water until desired temp (85 for meso and 105 for thermo). Add a small amount of dvi culture and let it set at temp over night. If thermo, I put it in a cooler filled with 110 temp water so it stays at the right temp......in the morning, the milk is pretty much yoghurt and works perfectly. We use skim milk for our breakfast cereal so it's a small price to pay. As far as I can tell, even with an expensive culture to cost is pretty negligible.
This whole process, other than swearing at the ExStick, takes less than 45 minutes the night before the make. Yes, you save some of the DVI culture, 1/16 tsp vs 1/4 tsp, but that is not the point. You are making a nice active starter that gets to work right away vice waiting 30 minutes or more to "wake up".
Bottom line - cheese making is fun. Way fun.
Linuxboy - I'm really into the mechanics (although I'm a physicist, I still really appreciate the science behind my obsessive hobbies....What texts are out there to help me move toward the understanding of what is really happening in a cheese?