Someone did a study on .50 cent pick 4's versus $1 pick 4's comparing the payoffs with respect to the parlay value. I can't remember where I saw it but I think it was on horseplayerdaily.com, and essentially the result was the chalkiest of pick 4's paid slightly more than they would have with a $1 minimum and medium-high payoffs (something like $600-$2,500 for a buck) paid slightly less. This result makes sense IMO- people play more combinations so the formerly overbet chalky combinations that everyone have get a boost and the combinations including perhaps one outlier which can now be covered with a lower budget drop slightly. I'd guess this study would translate to pick 3's as well.