Book an apartment or chalet
Most rentals are cheaper than hotels. You either go out for dinner, or cook your own meals. It's no problem to shop for groceries in Grindelwald, so cooking can be part of the fun. There are many restaurants in Grindelwald as well.
A rental at walking distance from the main rail station is most convenient. Grindelwald has two more stations called Grindelwald Grund and Grindelwald Terminal, but they're outside of the center. The main station is an easy starting point for trips into the mountains, including a visit to the Jungfraujoch.
Note that Grindelwald is hilly. If your apartment or chalet is somewhere along the streets Dorfstrasse or Spillstattstrasse, the altitude difference during your walk to the station is mostly insignificant. Rentals farther away from these streets could be up to 100 m up or down the hill. There are buses and taxis to get there.
Interhome offers thousands of holiday homes and apartments across Switzerland. They offer discounts on both early and last minute bookings. That makes the Interhome website a good place to start your search:
https://www.interhome.com/switzerland/: all holiday homes
https://www.interhome.com/switzerland/early-booking-discount/: find the discounts for early bookings
https://www.interhome.com/switzerland/last-minute/: find the last minute offers