It largely depends on the handle, Reno. There's a favorite/longshot bias that's overall prevalent in horse racing.
Just to illustrate...
In WPS pools, the longest longshots in each race are (blindly) overbet returning an ROI of -45.601%, -45.112%, and -52.281% while the favorite returns are -16.758%, -12.856%, and -12.470% YTD in thoroughbred races (at tracks with more than 200 races).
Meanwhile, a low volume track like Los Alamitos has better longshot returns than favorite returns YTD.
Of course, each race is individual and varies, but overall that gives you a bit of an idea. To answer your question directly, I haven't done much analysis on exotics yet. I would be surprised if it were much different though. Although, where there are Pick-6 rules (like at Gulfstream) where only one winner takes the entire pool and multiple winners receive only a percentage of the pool, it may shift those numbers a bit.