the missing CD's are a bummer, especially the White Album because finding this in Mono is so hard. you do have Sgt. Pepper and other albums so I think you made out okay.
Well, the bad news is, as far as I know none of the mono versions are available separately, so you might have some trouble tacking down the missing C.D.s (Best of luck in finding those) But I do think it's cool that you were able to pay only $20..00, PLUS you got Abbey Road and Let It Be throw in for compensation. Fun fact: Abbey Road and Let It Be WERE actually available in mono, but they were made especially the island countries of The South Pacific, where many people were so poor that they didn't have stereophonic record players. However, these were fake mono. This was known as "Fold Over" mono where you take a stereo mix, and rechannel it so everything comes out of one speaker. I've never owned one of these albums, not ever heard one, so I can't comment on the sound quality, but they existed at one time. Again, best of luck finding the missing mono versions from your collection, because they are quite unique.
If things look to good to be true, mostly it isn't true. I don't know if you want to have a fake set just to see one, but if you did want an original ... there are a lot of videos on RU-vid with warnings. Tru cdjapan to find the missing ones. Good luchmk and take care.