When my friend was revolver shopping at a gun show with me he found an older Taurus Model 66 for $300. Those older Model 66's tend to be good ones. He also found a used Armscor for $180. Both were in good shape.
The days of widely available $200 used K frames are long past; I am assuming that those comments are attempts at comedy.
I am also assuming that we are sticking to absolute max $300 OTD. There is not much you can get for that price by running out to Academy and buying something brand-new. Those little Heritage SA 22's come to mind.
For Gunbroker, $300 OTD would be a $250 or less winning bid - plus about $25 shipping and $25 FFL fee. This is not impossible, but it takes patience. In the past few years I have found some in this price range, but in each case it took patience - usually a couple of months of "stalking". I will list some below.
Two HR/NEF snub revolvers in 32 H&R magnum, both in very good shape, each less than $150 winning bid (I wanted to check out the caliber). A Charter Arms 32 H&R magnum snub in excellent condition for around $220 winning bid - apparently no one wanted the pink one. Two 100-year-old S&W revolvers with poor finish for winning bids of less than $150 apiece - a 38 special K frame and a 32 long J frame - they are both ugly, both work fine, and the 38 was a long search indeed. A Ruger Single Six with poor finish and a small part missing for around $125 winning bid - all it needed was a bottle of cold blue and $25 worth of parts (my crowning achievement in bargain shopping, and it was a VERY long search). There were also a couple more 22's. (I won't get into the semiautos, but I have also scored quite a few of those for $300 or less OTD.)
If someone wanted one right away, there are usually some older Taurus military surplus 38 specials for $200 or so. I think they are Models 80, 82, and 83? They might be kind of worn, but I would expect them to be functional.
It's true that you get what you pay for. But time, patience, and knowledge are also means of payment, and if you add in a moderate amount of money, you can get revolvers in that price range that function well.
Here is a gratuitous "after" picture of the Single Six 22lr. $125 bid + $25 shipping + $25 FFL fee +$25 parts and shipping + $10 cold blue = $210 total. You can see by the turn line that it has been shot a lot, but it locks up tight and is extremely accurate. Some days I shoot my Buck Mark better, some days I shoot the Single Six better.