I got an offer for a *deal* on a cab back to LAX from DLR, it would have been $75. I felt it would have been a bargain (but I already had travel arranged).
There's also Super Shuttle, which is about 16 pp from LAX and 10ish, I think, pp from SNA (= Orange County = John Wayne airport). If you are looking into SS, use the hotel name to get your quote. Do NOT use the zipcode, as the rates will be significantly higher.
There's also Grayline's
Disneyland Express, which is a coach bus. For our family of 3 the bus is cheaper than Super Shuttle, but the more people you have, the more of a bargain SS becomes over Express. If you book the DL Express online you get a few dollars off...and I just found that if you book the vouchers (at least for right now) through getawaytoday.com there's an even better deal. SNA again is cheaper than LAX.
And cabbing it from SNA can be a 40+ flat rate FROM the airport...generally you have to go by meter on the way back, and that can be more.
It's REALLY good that you're looking into all of the expenses instead of just assuming they are about equal! I messed up by booking a flight into Ontario, thinking SS was the same, and boy oh boy was that a MISTAKE. SS from/to Ontario is very very expensive.