$345 USD for a bare bones refurbished (used) A1200 from amikit seems pretty inflated to me. That's more than I paid 15 years ago, and it was brand new with manuals, software bundle,etc.
Although you are getting a warranty but still that's really high. $50 for a 4GB hard drive? Ouch.
Your best bet is to post to all of the forums... then go with someone who has a lot of posts and a good reputation.
I got my A1200 from another amiga fan for $150 USD with 68030 accelerator and everything, in the original box. Excellent condition too. Then recently I got a 1084s-D1 Monitor from another person on this forum... $40 no shipping required.
murple is right about the inflated prices... I've seen people trying to sell 1084s monitors for $150. You will not get a good price on ebay unless there is a soccer game during the auction end.