One of the biggest problems for the yearbook staff would be money. If the batch size is large, then funding can come from the students directly without any need for solicitations. Another plus for large batch sizes is the fact that the more yearbooks you order, the cheaper the per-unit price becomes.

Small batches (less than 200 students) are disadvantaged when it comes to pricing and funding. My batch, PCGS 1998, has exactly 72 graduates. Our cost per yearbook (P 1,000+) per copy is too high for the entire amount to be distributed between the 72 graduates, with the high costs of graduation and other expenses. Our only recourse, and the recourse of any yearbook staff plagued with small batch sizes, was to solicit from advertisers.

Usually, the printing press which is contracted to print the yearbooks will print the solicitation letters as part of the package. In our case, we printed our own solicitation letters (available online for reference purposes) since we have not yet chosen a printing press, and we needed to raise funds.

Exactly how much funds are available for use determines the quality of the yearbook. For example, one cannot expect to have the entire publication in full color on a shoestring budget. 
Money (and the lack thereof) can make or break a yearbook, so a responsible custodian should be assigned to take care of the finances.