wrong again, although I don't think you know it. Macs are a terrible choice here because PCs are the target platform, and applications and software are designed and tested for them.
It sounds like your IT staff made some poor decisions. If you are in a situation where you've tied yourself to one vendor, then you may be correct about PCs. However, I recommend you look for software that follows standards and isn't made for a specific version of a specific application on a specific platform.
And in addition, Windows is light years ahead for any sort of administration--in both speed, convenience and simplicity--for any size organization (and would be more efficient the larger the org) than Apple computers.
Not sure what you mean here. Remote login, controlled updates, automatic backups, MS Office, ERP software, etc., etc., etc., is all available on Mac too. Again, this is a dated argument.
And did I mention? The $500-1000 different PER computer cost isn't exactly in Apple's favor.
That's an easy stat to toss out, but I'd challenge you to back it. When you go spec-for-spec, Apple's hardware isn't much more expensive (sometimes cheaper) than the PC alternative. And there's the cost of support to consider too. In general, you get what you pay for. If you buy a cheap PC, it's probably going to cost you time and money to keep it running. If I'm getting paid $50/hr, it only takes a day of me screwing around with my quirky PC to cover your price gap (if it even exists). You've got to look beyond the sticker price.
Anyway, best of luck to you.