Writing is bought by the word more often than by the outcome, which is why so much commissioned content is competent, generic and useless. The difference between writing that works and writing that fills a page is almost entirely in the brief and in whether the writer has access to someone who knows the subject.
The brief determines the output more than the writer does
A brief worth writing states who the reader is, what they already believe, what you want them to do, what evidence supports it, and what must not be said. Without those, a writer produces something plausible from public sources, which is exactly what your competitors' agencies also produce. Require a briefing process and expect to spend real time in it, because the alternative is paying for words that could appear on anyone's site.
Access to expertise is what makes content specific
The content that earns attention contains something only your organisation knows: a number from your own operations, a method you use, a mistake you learned from. That requires the writer to interview someone who knows it, which costs your people time and is the single biggest predictor of whether the output is worth publishing. An agency that never asks to speak to anyone is producing summaries of what is already online.
Volume pricing buys volume
Per word and per article pricing optimises for throughput, which is appropriate for genuinely commodity content and destructive for anything meant to persuade or rank. If you want content that earns links and references, expect to pay per piece at a level that funds research and interviews. Decide which kind you are buying and price accordingly, rather than buying the cheap kind and being disappointed it did not perform.
Ownership, claims and the search dimension
Require an express written copyright assignment, since under 17 USC 101 commissioned writing is not automatically yours, and require confirmation that work is original. Any claim made in content should be substantiable, with testimonials and endorsements governed by the guides at 16 CFR part 255. If search performance is part of the objective, Google's own guidance on hiring an SEO is worth reading before agreeing what success means.
Questions people ask about copywriters agency
Why is commissioned content so often generic?
Because the brief was thin and the writer had no access to anyone who knows the subject, so they produced something plausible from public sources, which is what every competitor's agency also produces.
How should writing be priced?
Per word suits genuinely commodity content. Anything meant to persuade or earn references should be priced per piece at a level that funds research and interviews, because that is what makes it specific.
What should we own?
An express written copyright assignment, since commissioned writing is not automatically yours under 17 USC 101, plus confirmation the work is original and that claims within it can be substantiated.