It's a buyers market in the motor boat world at the moment. We looked at one recently marked up at £24,950(6 berth/twin diesels); the salesman said 'make an offer, you'll get it for 18 or 19 thousand'. We actually bought a different one for a bit more, but still a bargain.
You can get a 4 berth for as little as £6,000 to £10,000 at the moment, especially if it's petrol engined.