Belive it or not, OEM pricing is ofen 1/3 retail or even much less; especially in the volumes someone like MTD runs.
Now does the MTD-B&S, MTD-Kohler, etc, contract allow wider tolerances or cheaper parts than the "catalog" products? I don't know; if so, there's probably something different with the model# to indicate the MTD OEM. Believe it or not, with the "sorting quality" costs of <font color="blue">Seconds?</font>, I don't think it's in B&Ss interest to do. Cheaper componts almost has the same theory, but on millions of items, those pennies do add up. Regardless, except in cases where "this serial number to that serial number" had a factory defect, poor engine choice is the final product mfg's responsiblty as well if not more so.
BTW the neighbor was out tilling 1/2 acre of pasture with a Sears LT; he got it running again, but it was sounding pretty sick for a while. I pitied the machine more than him!
As far as those bitten twice with anything, I can't blame them for being shy [I'm afraid there aren't going to be converts from either direction coming out of this thread]; though, I too appreciate specific details over blanket statements [barring this thread of course]. To make matters worse, in the "consumer lines" the sales are there; I'm afraid neither MTD nor anyone else is out to "sweeten people" on them. Fancy features and names like Kohler might "charm" a few new buyers, but I don't see quick changes for those already opinionated in either direction!
Chad