I'm not sure what 'reasonably priced' means to you, but if you're looking for a good combination of comfort, room size, location and price then the 4*Takanawa Prince (booked through Utell.com) is extremely hard to beat. It’s right by Shinagawa Station, 20/25 minutes from Yokohama and about 10 minutes from Kawasaki. NRT is less than 1.5 hours away by train or bus. There are few places in Tokyo where you wouldn’t be able to get to within 20 minutes.

The kanji for Shinagawa station is also very easy to recognise (3 boxes & 3 vertical lines)

EDIT:- I often visit Yokohama, but I've only stayed there once overnight (at the Washington Sakuragicho – 10,000 yen for a tiny double but you get a truly spectacular view – please note that I am NOT recommending this particular establishment as being suitable for your needs).

Yokohama bayside was absolutely dead by 10:30pm/11pm. We found a 24hr Jonathan’s a and a late opening Mosburger but that was it. Even the convenience stores were closed.

All I’m saying is don’t expect much nightlife in Yokohama if that’s where you decide to stay.