Personally, I'd choose the RJ Martin Machine midtech. It's one of the best production flippers I've found and they retail around $350. USA made too. Don't have a photo of mine handy but looks just like this:
Shady's right, the RJ Martin/Three Rivers Manufacturing Machine Flipper is a great knife that fits
B
Blade_Lust
's budget criterion. It retails for $385 at ME and is also available in a fluted handle version elsewhere. I prefer my MEFP version over the fluted, even though fluted ti is one of my favorite handle patterns.
TRM's quality is excellent and RJ personally fits the detent ball in each knife, adjusting the flipping action, and adding his stupidly sharp convex edge by hand. I do have pics of mine available.
On another note, I agree with others that have posted here that the $300-400 range is a bit of a "no man's land" for quality mid-techs with most of the predominantly-considered makers' knives falling in the $400-500 area. $200-300 is mostly occupied by production knives like ZT--great knives, but not quite mid-tech quality--and quite a few knives by the quality Chinese makers, with which I have no experience.
Again, to echo others, buying on the Exchange opens up the $400+ knives to the OP's desired price range. Not only does buying there reduce price, but the knives are "pre-screened" as most all BFers are honest about the quality of their offerings. I've bought the majority of of my mid-techs on the Exchange including all my CRKs, some of my Hinderers, the RJ Martin, my WC/Les George Eagle, a Strider SNG, and others, all but a couple of the CRKs having been acquired for less than 4 bills. I was lucky to find my Olamic Wayfarer 247 on sale new at just under $400 but those knives do show up on the Exchange within the OP's budget. The 247 is another great knife that comes in many varieties of finish. Here's mine....