Additionally, large plants can spread compliance costs

Among the myths taken as fact by the environmental managers of most corporations is the belief that environmental regulations affect all competitors in a given industry uniformly. In reality, regulatory costs—and therefore compliance—fall unevenly, economically disadvantaging some companies and benefiting others. For example, a plant situated near a number of larger noncompliant competitors is less likely to attract the attention of local regulators than is an isolated plant, and less attention means lower costs. Additionally, large plants can spread compliance costs such as waste treatment across a larger revenue base; on the other hand, some smaller plants may not even be subject to certain provisions such as permit or reporting requirements by virtue of their size.

Could someone please paraphrase the bold part?

“Compliance costs” are the costs needed to comply with government regulations, the example here being treating your waste to eliminate pollution. “Revenue base” would be the total revenue of the plant. The sentence is saying with a larger plant, the compliance costs will be a smaller percentage or proportion of the total revenue. For instance, if a waste treatment system has a total cost of 1 million dollars, this will hurt your profit less if your total plant revenue is 100 million dollars instead of 10 million dollars.