In 2012 we stayed at pre-cruise (and post-cruise) at Hotel Continental on Las Ramblas. I think there is a pricier one a few blocks away.
For us it was ideal location. It was comfortable, not quite as fancy as the pictures imply. The hop on hop off bus routes all started from there. 24 hours free light buffet, beer/wine, ice cream… perfect when you arrive jetlagged (One day we stopped in for lunch before switching hoho route).
In 2018 we returned with 2 other couples and rented 3BR/2bath airbnb. Decent rate (at the time about $100/couple per night), a bit quieter. There was a bakery / sandwich shop on first floor - very handy. Stayed 4 nights. Did a lot of walking but sometimes used train or taxi.
Here is a link showing both Hotel Continental in Barcelona. The Las Ramblas one we liked was recommended by Rick Steves. The Palacete was near our airbnb on other visit, Plaza Catalunya - nice area too. https://www.hotelcontinental.com/our-hotels
Cost will depend on date and number of people. Old (but nice enough) building, only a small glass elevator. No biggie to us since some of us preferred stairs anyway. Have not checked recent reviews. Feel free to PM me with specific questions.
Apparently there’s a large oncology convention during our exact dates (Sept 13-17 inclusive) - which adds a new layer to finding something great. I’ve found a few good listings, and we’ll book as long as there are decent cancellation options.