Bart van Zon put together a short blog post describing why some web developers, who chose Mac as their development platform, might attempt to avoid testing their product in Internet Explorer.

Here is one of them:

“It’s expensive getting hardware to test on, taking time to test it, making sure you have a Windows installation”

Really? Let’s break down the costs.

To invest in a Mac system:

• MacBook Pro – starts at $1199 for 13-inch. (source) OR
• Mac Mini – starts at $599 (source) + display at ~$140 (source) + ~$16 keyboard (source) & $8 mouse (source) totals to $763

Here is for Windows PC:

• A decent modern laptop for $400 (source) (pre-bundled with Windows 7 Home Premium)

But let's go beyond that - Macs have Bootcamp, so your investment might be reduced to simply getting a copy of Windows for $120 (source). Or, you might go with what Wes MacDonald suggested in the comments - which results in an additional investment of $0 (download testing VHDs here).

If you are a serious developer who invests his time and effort in creating a solid platform, using hardware priced above average and consider Windows to be a breaking investment, your argument is invalid.

PS: Developers, you might want to also read this.