Take it slow, sounds like you are in the same position I am in. I've spent more money than I probably should have, but then again I've been tempted but have refrained from spending much more. By taking it slow I've gotten my stuff inexpensively and have no real worries - if I decide to bail out of this hobby, I can definitely get all my money back.
That's my thought as well. I haven't done much with my Amiga 2000 since I restored it, so I don't want to spend tremendous amounts of money in case I never really get back into the hobby. Still, I've had a good time so far.
Like you it seems, what's driving me is the challenge of getting these things up and running and the nostalgic appeal. Who knows how long your interest will last, so don't go overboard. I'd never pay the prices some of these products are demanding - just not worth it for me!
Yeah, the prices for USB and ethernet are just insane. I understand that it is a very small market and the companies making them have to make money off of them, but the prices are still too high IMO.
For my part, I focus on classic Amiga stuff anyway. I have no interest in running 4.0 or above. If it can't run on a classic machine, it isn't something I care about. USB or ethernet would be nice to have just to aid in transferring files, but I can get SCSI ZIP drives cheaper and I have an old USB ZIP drive attached to my PC so transferring files is easy.
Unfortunately I now have more "toys" than I have time to play with. Amiga 4000T, 3000, C128D, C128, C64C and soon an Atari 800.... ugh... it's an addiction! 
If I keep up this hobby, I think an A1000 and A4000 will eventually find their way into my home. I'll be redoing my mancave in the next year or so and when I do, I may make it more like Blake Patterson's "Byte Cellar" and I'll have more room for my machines. My wife will just roll her eyes but she'll get over it.
I've also got another project I'm considering, and it will be a long and hard project to complete. Basically, I'd be building another A2000 from the ground up. I'd be buying individual components and building it completely from scratch. The reason I say it would be challenging is because I do have another A2000 motherboard that has some significant battery damage. It is repairable, but I'd need to remove some sockets (like the 68000 socket) and solder on replacements. I have to decide if I really want to do this or not, as there is a complete A2000 case up on eBay right now.
Just remember if your battery dies it will no longer boot to the CF card slot until you boot to floppy and re-enable LUNs. You can, however, boot to the CF card in a PCMCIA adapter (if you have one) if the battery dies.
Good point. I should probably use a CF with an adapter as my primary boot drive anyway. Right now I've got a vanilla install of 3.1 on a 3.2 GB SCSI drive and I'm not sure how long that drive will last. I'll probably have to do the same thing to my A2000 as well, as I'm not sure my 20+ year-old 52 MB Quantum drive will last much longer.
