I want to convince my manager and (probably) his manager that a project needs to be scrapped and we need to purchase an off-the-shelf solution.

Somehow it was recommended that, rather than use a pre-built solution like FogBugz to do our task/issue tracking, we should roll our own. Now, this is definitely not a core service for us. The current price to purchase an unlimited site-license for FogBugz for our server is $15,000 USD for the Kiln-integrated version. $10,000 for the standalone version.

At the current rate we charge per developer hour we have now spent $35,000 on our project which is nowhere near as useful or complete. Even if you're just looking at "actual" developer cost (just our salary) we've spent at least $17,500 USD. I know there are other related maintenance costs, but they'd be closer to $2,500 than $20k. Of course our system isn't even *close* to as full-featured as FogBugz.

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Now here's the real issue - I'm an extremely junior developer (< 6 months, fresh university graduate) at my company, and employees who've been working since before I went to college are the people who made the recommendation that we do the development in-house. A system that has close ties with our project is my direct manager's baby, and I'm not sure how much he emotionally has invested in this - he did do some initial leg work before we started the project.

I'm worried that my junior position makes me fairly vulnerable, but more particularly that I'll come off looking like a snotty-nosed know-it-all. I know that I might be discounting some of the other expenses here, such as servers (cheap!) and administrators (not so cheap) to maintain the system, but I'm almost 100% certain that I'm not discounting it to the tune of around a half-years' salary.

I have a fairly good repoire with my manager, so I'm sure that will help. I'm also aware of decision fatigue, so I'll make sure to bring it up in the morning or right after lunch. What other skills/data should I bring to the table to increase the chances that I'll be taken seriously?