So I just did a quick check on the purchase vs retail price for my pieces. The problem is that the pieces that I have are from different years, so normalising the retail price is a bit difficult. But let me summarise what I found. Just for reference, I have only bought one watch from an AD (purple Monaco) - rest are from private sellers.
1. H02 (CBL) models: I have the purple Monaco (CBL 2118), which I had bought on retail when it released. The other is the GPdH Monaco (CBL 2114), which I bought in December at a 25% discount from a private seller
2. Calibre 11/12 (CAW) models: I have all 4 non-LE C11s so it gets interesting here. I bought the CAW211P (blue Monaco) and CAW211R (Gulf) at a 30% discount. Both are 2022 models. The CAW211C & CAW211D were purchased at almost a 40% discount. The 2 LEs in this category are the CAW211E (green Japan Monaco) and CAW2116 (Singapore numbered) which were purchased at a 20% discount from retail.
3. Older (CS & CW) models: It's very difficult to tell the discount for these as I wouldn't know their retail due to their age. The 2007 catalogue prices the CW2114 (python) at US$3300, and I had bought it for £2000 in 2022 (+ £550 for service), so that's above retail. The other two are the CS2111 Monaco Grand Prix and the CS2113, for which I don't know the retail, so can't compare.
4. Others: I have the CW9110 (Monaco 69), which I bought for shit cheap, but am spending the same amount on it's repair, so that comes to about 50% discount from retail (inc. cost of repair). The other is the 40th anniversary Monza (CR2080), which I bought for £2200 (no box or papers) so that was also at a heavy discount.
A few inferences that I make are:
a. The flagship models (blue and Gulf Monaco) can be purchased at a relatively lower discount.
b. Non-LE's will attract a higher discount than LE's, and marginally higher discount than SE's.
c. You'll get a higher discount (even on LEs) if they reach a certain age. For me, that age is at least 2 years old.