CPA or CPC or CPM?

Advertisers should like;
PPS >>> CPA >>> CPC >>> CPM

Publishers should like;
PPS <<< CPA <<< CPC <<< CPM

Sometimes advertisers prefer to CPM when it is really "low" and CTR&CVR is high enough. When CPM is $0.05, CTR is 5%, and CVR is 5%, 100,000 imps generate 100,000 * 5% * 5% = 250 conversions just with the cost of $5, and this calculated CPA would be $0.02. At this time, CPM is more reasonable than buying traffic by CPA$1.00.

Sometimes publishers prefer to CPA when it is really "high" and CTR&CVR is high enough. When CPM is $0.30, CTR is 5%, and CVR is 5%, 100,000 imps generate 100,000 * 5% * 5% = 250 conversions just with the cost of $30, and this calculated CPA would be $0.12. At this time, if CPA is mote than $0.12, a CPA deal is better than selling traffic by CPM$0.30.

However, they are hardly realistic...CTR will not be so high and CVR will not be so high.

As a result, advertisers should look for a campaign closer to PPS and publishers should look for one closer to CPM. Compromising the both interest, CPA or CPC campaign will be the better options for both party.

What do you think?