The problem is that their brief is too vague and the real issue is communication.
At no point is it clear that they’ve discussed off the shelf solutions, or infrastructure (storage, server hiding, CDN etc).
If they had, then they either messed up because 15k over two months is too high or too low. It’s squarely in the: “nobody has actually defined the project territory” for me.
Yes, a Wordpress solution would work, but then why even budget 2 months for it, unless bespoke design is involved. Again that becomes a: this is too low or too high to be realistic