Almost always? Nope. In my experience, it’s close to never. My last cruise was a standard one week western med cruise out of Barcelona. Inside cabin, solo supplement, with internet and drink package for $730. I could have added speciality restaurant package for <$100. R/T flight out of Boston was $500.
Cheapest week I can find on Oceania anywhere, anytime is 4238€. That doesn’t include flights. Granted it’s a balcony room, but I’m sure I can find the equivalent on a mainstream line for a fraction of that price.