Related to your question there is a very interesting discussion on LinkedIn https://www.linkedin.com/groups/Cost-versus-ASIL-2308567.S.92692199

There are differences on cost calculation whether you are going for the avionics or the automotive domain. So for the avionics domain there they were proposing

Level E - No safety impact, x1

Level D - Minor impact, x3

Level C - Major impact, x5

Level B - Hazardous, x9

Level A - Catastrophic, x10

For  other domains they propose  the following

IEC 61508......ISO 26262.......Effort increase

..SIL 1.............ASIL A............5..-..20%

..SIL 2.............ASIL B...........10..-..36%

..SIL 3.............ASIL C...........20..-..60%

..SIL 3.............ASIL D...........40..-.100%

Thanks for the answer !

This seems to be close to what I've found so far (considering the differences between the standards), I also posted this question on the ARP4754 group on LinkedIn and they have given some good insight as well.

https://www.linkedin.com/groups/DAL-costs-evaluating-allocations-4074780.S.5858669498474725376?qid=12058e83-6ada-4fe3-a2c0-481b1df8f116&trk=groups_items_see_more-0-b-ttl