I had dinner last night with someone familiar with Cessna's process of replacing the Honeywell avionics suite in the Sovereign with Garmin. Approaching $100 million to do the switch. Some recovered by a lower ongoing cost of Garmin in each aircraft, but still a big chunk of change.
I wouldn't expect Bell to undertake that level of expense on the 429 unless they expect to sell a lot of units. Better luck would be having Bell lean on RK to do some more realistic support pricing.
Many Citations are on Pro Parts, fixing price per hour, and it is on Cessna to worry about the costs from Collins, Honeywell, Garmin etc., on spares.