Not the most traveled here - but I've done perhaps 12 cruises - anything from Mainstream lines like Royal, to lux lines like Regent.
If 100% of the goal is price, I'd look at CruiseCompete dot com. Quick real quotes, good deals vis a vis discounts off sticker price of cruise. However -minimal to no personalized service - not saying that is a need, just pointing it out. I have used them twice - mind you that was years ago but they still are in business.
I personally like having someone to call. So I use my travel agent and we have an unwritten rule that I get "OBC" on each cruise -- that means OnBoard Credit for spending. I get 6-8% OBC each cruise - in ADDITION to whatever the cruise-line is offering. The 6-8% comes out of the travel agent's commission. (If I spend $10,000 on a family cruise, I get $700 to spend on the ship). Again YMMV - my 1st agent - when I knew nothing about cruising - - would send me a $50 gift to my room. No thanks I prefer the nice OBC instead. We don't buy "stuff" on the ship.....but shore excursions, specialty restaurants add up. I've heard of others getting more OBC than me - but my travel agent is always on cell, we meet in person at times, and if needed he takes care of small requests.