I’ll illustrate a possible scenario and approach (and this is after you discuss TCO as well as using the term “opportunity cost” with management).
Set-up: the business is standardized on Adobe CC Suite (I picked the obvious example). Volume license is up to par, deployment strategies in place, and even some internal documentation exists (!!!).
NewGuy started Monday and his first request was to ask for the CorelDRAW suite*. You have no volume licensing agreement in place for this, and have not planned a deployment strategy (if you’re using SCCM or similar, it wouldn’t be that difficult, but I digress).
You have two approaches:
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NO!
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Why?
The first answer is obvious, and if I know this community well enough, it’s the knee-jerk reaction most of us will have. 
The second challenges the requester and the management to justify the request. You’re not saying “no,” but you’re also not saying “yes.” You’re putting the responsibility for justifying the immediate and hidden costs on NewGuy.
“What can you do with CorelDRAW suite that you can’t do with the CC products?”
The presumption here is that the job posting specifically listed Adobe CC products, and that was discussed in the interview. So for this scenario, we assume that the candidate has specifically said “I am capable of using Adobe CC products.”
NG: “Well, it’s just easier for me to use the CorelDRAW suite.”
You: "OK, I get that, but it’s $400 just to buy the suite. We also won’t know how many copies we’d need if we open that floodgate, so it could be up to 5 or more copies (aside: you’d know your company culture better than us, to determine whether the presence of this alternative software would cause others to start sniffing around). It’ll probably take about a week for the PO to get cut and sent out, unless we use a P-card. Then, it’s about 4 hours of my time to get the software, learn how to deploy it, TEST the deployment, and then unleash it to you.
At the same time, if you run into problems that are centered around CorelDRAW, support would be your responsibility, as we don’t have the expertise in supporting CorelDRAW (or it would take XYZ hours to get to that point, which means time we’re not spending on mission-critical projects).
So based on all of that, NG’s Manager, is CorelDRAW still the way to do even though we’re already licensed for and have the support structure in place for Adobe?"
This way, you’ve articulated your concerns without sounding like an obstructionist jerk, identified the costs, and laid the responsibility for the final decision in the big picture on someone else’s shoes.
- I understand this particular request personally. I’ve used Paint Shop Pro since version 3, when it was a JASC product. After v9, JASC was acquired by Corel, but PSP remained largely the same. When PSP introduced vector drawing in v6, I had little to no need to learn Photoshop and Illustrator. I’m not a pro graphic designer, but do some image manipulation work here and there. With enough tutorials out there, I could touch up photos using the same tricks in PSP as Photoshop. I’m more comfortable with PSP, and it’s a hell of a lot cheaper.