I am planning a trip to Europe this coming spring. What is the best and economic way to get to Jungfrau from Barcelona? Where to fly to and what city to stay in?
What is the most econmic way to get to Jungfrau? I've heard about Jungfrau Travel Pass. Is it the most economic way?
Any suggestions would be appreciated.

Economic travel to Jungfraujoch is a contradictio in adiecto.

A full fare ticket from Basel airport to Jungfraujoch and back costs 370 CHF (about 400 USD )/pax.
There exist many specific railpasses and saver tickets, but as long as we don't know your itinerary for your whole stay in Switzerland,
it's not possible to give any advice.

Thanks for the reply. I had traveled to Switzerland (drove from Geneva to Zurich) before, but at the time we missed Jungfrau.
This time I will be in Barcelona in May(2025) and will go to Munich. So I am wondering if I should stop by Switzerland to see Jungfrau. That's why my question was vague in details.
So in this case what would be the most economical way to visit Jungfrau? Fly into and out of what airport? I understand there are two departing towns for the trains toward Jungfrau - Grinenwald and Lautenbrunnen.

This wouldn't be a minor or short detour on the way from Barcelona to Munich. It would involve multiple steps on two long journeys, each taking most of a day, and $$$. And, in May, views of the Jungfrau are often obscured by clouds and snow flurries, so you'd want to plan on spending multiple days there to give you the chance of seeing the peak from below and enjoying the views from the top.

If you need to be economical then I completely respect that, but it's just about impossible to do that in this situation. Even if budget were not an issue, I think this isn't worth the time.

I visited the Jungfrau about 20 years ago. I had 3 days in Grindelwald so I watched the forecast and I went on a clear day. I took the earliest train up to avoid the crowds, which are surely worse today. I can't imagine a rushed trip just to go to the Jungfrau for a day. I think your time and money are better spent elsewhere. There's so much to do in both Barcelona and Munich, I would focus on those amazing cities.

This stresses me out just thinking about it. The Jungfrau isn't a simple detour. One just doesn't "stop by Switzerland" from Munich, let alone include the Jungfrau.

How long is this trip? If the Jungfrau is part of a longer stay in Switzerland, fine, but it doesn't sound like what you have in mind.

I fully second Jean, Mel and PM.
A ride to Jungfraujoch is always a waste of monmey. Even if the weather is fine.
There are furthermoe tons of other Glacier destinations in Switzerland, much cheaper and much easier to reach.

But in order to answer your question:
If you want to see nothing but Jungfraujoch and then go on to Munich, the cheapest solution would be (for the random date of May 15th):

Buy a Vueling plane ticket BCN dp 7.00 - ZRH ar 8.55 well ahead (fares start at 55 USD without luggage)
Buy a Swiss Saver Day Pass well ahead (costs actually 39 CHF resp ab out 45 USD
Buy a half fare RT Ticket Gindelwald - Jungfraujoch (at any time) for 101 CHF
Buy a Flixbus ticket Konstanz - Munich for 14 CHF

Timetable:
BCN dp 7.05 - ZRH ar 8.55 (covered by plane ticket)
ZRH dp 9.45 - train -Grindelwald Terminal ar 12.33 (covered by Saver Day Pass)
Grindelwald Terminal dp 12.40 - (gondola and cog wheel tunnel railway) - Jungfraujoch ar 13.41, dp 16.46 - Grindelwald Terminal ar 17.06 (covered by RT ticket)
Grindelwald Terminal dp 17.21 - train - Konstanz ar 21.34 (covered by Saver Day Pass)
Sleep at Konstanz
Konstanz dp 10.35 - Flixbus - Munich ar 14.20 (covered by Flixbus ticket)

I thank you all who took time out to reply my post. As most of you suggested or implied, it would be better if I postpone the idea of visiting Jungfrau on my way to Munich from Barcelona. I will make a separate trip to Switzerland which will include a trip to Jungfrau.
Thanks again.

I'm glad we could help. Enjoy your trip.