IBR can be great. Perhaps I can elucidate a bit through explaining my own situation.
I am on IBR and have been since finishing grad school three years ago. I pay about $300 in loan repayments each month. That's about $3,600 per year.
I have about $90,000 of federal loans, which will be forgiven after 20/25 years if I am still paying them back.
I have access to a 457b and I put money into that, enough to get my income down to about $47,000, which for me is the sweet spot as someone who files tax returns as single. With a $47,000 income, my taxable income is about $37,000, about the cutoff point for the 15% tax bracket. So my marginal tax rate is 15%.
Since my taxable income if about $37,000, my IBR payments are scaled accordingly - I will pay 10% of my taxable income, which is $37,000/10 = $3,700 per year. Divided by 12 months, $3,700/12 = about $300 in student loan repayments each month (really about $308 but we'll call it $300).
In this way I am contributing to financial independence slowly and surely through a 457b retirement account, and paying less than $4,000 each year in loan repayments.
Two other factors make IBR particularly appealing for my situation.
I will qualify for Public Service Loan Forgiveness after 10 years of these IBR payments. So that's about 10 years of paying about $3,600/$3,700 each year = about $37,000 in total student loan payments, for an original principal upon graduation of about $90,000.
The other factor that makes IBR appealing to me is that my graduate school allows for a Loan Repayment Assistance Program, so long as my income is below something like $55,000. They use adjusted gross income, not total income, meaning that even if my salary is above that amount, contributing to a 457b will knock it down so that I qualify. A Loan Repayment Assistance Program (LRAP) is a program in which your graduate school/undergrad gives you money to pay back your loans, so long as you work in public interest. For my adjusted gross income, they'll pay me a maximum of $3,000 per year to pay back my loans, for up to five years. So I'm only paying about $700 per year for my loans after the LRAP check comes in.
All in all I expect to pay less than $30,000 for my student loans.
So IBR can be great, especially for those who are in public interest and have a high student loan principal. I might have gone to a different (more expensive) law school had I known about it all that time ago. Actually it incentivizes people to go to expensive schools, and not be very frugal. They could end up paying about as much as someone who cooks at home and lives modestly. Had I known about IBR while in school, I may have even taken out more loans and invested some of it into a brokerage account if that would have been an option (I'm not sure if that would be legal).