Ghuethuyue59
As you’re mentioning 2 days: Usually a saver day pass would not be cheaper than a regular single journey (point-2-point) ticket between Basel and Grindelwald/Wengen.
Note that Eigergletscher is already located in the ‘expensive zone’ of Junfrau Railways. As some reservation/priority boarding system is effective right now for Jungfraujoch, I’d suggest to get the Jungfrau Railways tickets between Grindelwald/Wengen and the ‘Top’ directly from their website, where you can also specify travel cards such as the Swiss Half Fare Card mentioned by Krist above, and check how they’d affect the ticket prices.
Even with only 2 travel days, a SHFC should usually already pay off if Jungfraujoch is involved.