Fairlay is usually a cent or so better on average than pinnacle and if you suck up the junk between the market maker and pinnacles price you can save a few cents more but very low limits.
example Pinnacle has -105 fairlay will probably have a 2500mbtc at -104.4 and it will have 1 or 2 little matches of -102 40mbtc and
-103.3 20mbtc so you would get those 2 small matches and the rest would be at -104.4
lots of people put the 1 cent better lines on games they like and lots of times forget about them and you can get some at a huge discount but they are usually at very low limits.
fairlay uses an api to adjust when pinnacle adjusts so very rarely any high limit stale lines
it would be a waste of time to offer a few cents better for a high limit because nobody bets there and 99 out of 100 would just sit and not be filled.