I spent all my life an omnivore, until the last two years I became vegetarian; 6 of those months vegan. I’m inclined to agree with you if you meant that a ‘satiated’ vegan diet is more expensive, because often the (lower demand / higher price) raw ingredients to make meals from scratch are more niche and varied.

However, once you throw (principally) dairy into the mix, including mass-market meat substitutes (such as Quorn which often contains dairy derivatives), your options expand to the point where it is easy to a) just drop the meat and increase veg. intake with supplemented dairy from common dishes or b) replace the meat with a price-competitive meat substitute.

If you did indeed mean vegetarianism in general then I’m keen to know why you think it is more expensive.

I’m with other commenters here that this is a weird cost-saving measure from WW, and that dietary choices should not be imposed on people like this (whilst acknowledging WW is a private company and can do whatever they want—- it’s just a strange way to force it on people IMO)