Certainly, with ongoing jobs, this is definitely true. For enterprise software, this customization is basically the bulk of the business. However, the article

Certainly, with ongoing jobs, this is definitely true. For enterprise software, this customization is basically the bulk of the business. However, the article is about a product with a single codebase, dealing with potential customers, rather than actual customers. (The auther doesn't specifically spell this out in the article, but that's how I interpreted it) That situation is completely different, as he isn't talking about building customizations into the contract, he's talking about customers who say "add this feature AND THEN I'll buy it (for the original price)." So you're right, but you aren't talking about the same thing at all, even though it may seem like it at first.