Bob -- yep, those straight parlay numbers are right on.
As far as the expected payout based on those win odds, it will vary slightly from track to track depending on the takeout. Assuming we’re talking the NYRA circuit, where WPS takeout is 16% and Pk3 & Pk4 takeout is 24%, the expected payouts would be:
Pick 3: 0.76/(.84)^3 = 1.282 x win parlay
So for $1 Pk3, the expected payout is $398 x 1.282 = $510
Pick 4: .76/(.84)^4 = 1.5265 x win parlay
So for $.50 bargain basement Pk4, the expected payout is $894 x 1.5265 = $1,365
Rocky