I fully agree with the Brichins' comment under your original question. You will not find the answer whether this is ethical on this forum, this is something that you can only find out yourself.
It is this whole business/revenue/end of year thing that makes me too think it reeks by some managers' attempt to fix the short term numbers to achieve their end period's targets and get a bonus, without any regards to potential impact on the relationship with the clients and long-term business.
This is something very typical, especially now in the time of aggressive cost savings, and tends to affect pretty much every area of business, e.g. I have seen some very nasty pressures for not paying invoices to suppliers before the quarter-end (let alone year-end!!!) to skew the numbers resulting in loss of service (impacting delivery to clients) and even suits from suppliers because T&Cs of payment were grossly breached.
Larger corporations typically try to fight this tendency by deploying trainings/e-learnings and internal whistle-blowing policies and to be honest what you describe is some of the prototypical cases of what these trainigs identify as suspicious situations. The general rule is if it feels fishy, you should raise/report it, and even if it turns out to be a non-issue, you should be protected by some non-retaliation policy (or legislation), provided you reported the problem cum bona fide (which does not mean it will not strain irreversibly your workplace relationships).
What to do... is up to you (as always:)) and depends largely on your work conditions. My general approach would be to raise this with your direct manager first in some polite and neutral way (but beware, it may also be their bonus at stake!) and perhaps they will alleviate your concerns by giving some very good and plausible reasons (like "3rd party techs are available but just run out of money, so if we order them, we won't be able to pay them, which is in my book unethical behaviour and I'd rather our company to swallow up responsibility even if it means loss of business for us") but if you still feel it is fishy, you can try escalating somewhere further in the business (if you are a large company, you may have a white line to report this kind of stuff anonymously) because somebody higher up might no be of the opinion that mid-level manager's bonus is worth a lost client. Also it may be just a bad business decision (somebody taking directives from Finance over-zealously without assessing the business impact), you never know.
Bad news is that either way, it can cost you your job:
If you raise it and delve into some shady corporate stuff, your manager may try to get rid of you (which again may be technically a wrongful dismissal but not sure if you want to continue the dispute at a court...) - this depends mostly on your workplace culture.
If you do not raise this, your company may lose clients and business and you may find yourself out of a job because of redundancy.