I understand that web developers are wary of buying boatloads of devices, but this is something that’s simply going to change in the next year or so.
Yes, buying a lot of devices will cost you a lot of money. But it’s simply an investment that you have to earn back from your clients.
Buying devices is not something you have to do immediately. It only makes economic sense if you’ve got enough clients that want mobile websites. On the other hand, you’ll never get such clients if you don’t invest in devices.
It’s a catch-22 right now. But that’ll change. Just keep an eye on mobile questions of your clients, and decide beforehand when it starts making sense to make an investment in devices. When you have two mobile jobs? Five? Whatever, just make a rule and stick to it.