You speak only the truth. Especially the low level, common spells (5-15). To put it in perspective, a professional scribe (scribe 6) trained in Magic Theory can copy 360 levels of spell texts in a season. That same scribe could copy a single level 12 summae in the same season of work. It seems logical that essentially the same amount of raw materials is going into each - i.e. lab texts are far less weighty than summae, in general. So the physical cost of the two should be little different. But a L12 Q12 Summae is 24BP, while 360 levels of lab texts are 72 BP. Granted it took a magus to clarify the lab text at some point, but in most cases scribes will be working from texts that have been clear for decades, possibly centuries.