It could have been more subtle (ok, much more subtle) but this is the same advice that has been given many times over, by many different members about many different products - you can get x cheaper from y. If he had said that "there are a few x suppliers you can consider, including y who are quite reasonably priced" would it be an issue?

If a mod wanted to promote or draw attention to a sponsor, fair enough, but I would be much more concerned if they were afraid to give their opinion or present alternatives. As pointed out, the sponsors can also reply.

I do appreciate that the mods might want to display a touch more diplomacy when discussing sponsors than the rest of us, but objectivity is really important.