I think Atari internal sales figures 3,384 copies being sold for Bmx Airmaster show the rarity is to high. I think it is a 9 as a result.
My proof is the attachment. It is an excel spread sheet. I recorded the copies of all Atari 2600 game sales in copies from 1986 to 1990 according to Curt Vendel's Documents.
If you look at 103A on excel, you will see BMX Air Master. That row shows the copies sold of the Atari published version of the game from 1986 to 1990. The 3,384 copies sold is the final total from those years.
I am willing to upload the Atari 2600 internal sales documents that Curt Vendel posted on Atariage if my excel spreadsheet if not enough proof if I get the okay from him.