The real story about scholarships is much much more complicated. Here’s how it works in practice:
The school (any school) is looking for a combination of three factors that increases the rankability of their student body. In practice, that means they want LSAT, GPA, and diversity. The particular combination doesn’t really matter as much as you would think, although high LSATs are more rare than high GPAs and consequently valued more by most schools. Boalt is one of the few schools that goes for GPA over LSAT.
The other factor is what the school needs based on the offers made and the probability that the student will accept the offer. This is actually what drives scholarships. Every school offers merit based scholarships, which are actually more like bribes to the student. Merit in this case means “scores that will raise our ranking”.
So schools like Harvard do offer the scholarships, and tuition waivers of varying amounts. However, having a high LSAT and low GPA is less likely to attract money at the 10 - 15 top ranked schools simply because they have a virtually endless supply of candidates with high GPA and LSAT.
At schools trying to increase their rankings, there is money available to people with only one high score, but it depends entirely upon the school’s needs. The key is to have your LSAT be higher than their target, so if you have, say, a 175 (unlikely), you will be above the target at every school, including HYS, by a good amount. In that case, even Harvard might offer you a discount.
The bottom 100 or so schools tend to offer a lot more full rides, but they generally offer a lower median of scholarship money.
As for full rides in general, they are somewhat rare, and yes, if you get high score on the LSAT with a low GPA, plenty of tier 3 and 4 schools will give you a full ride, which you would be an idiot to take. You can get them at better schools with good negotiation, but the truth is that in almost every case, the ranking hit you will take for a full ride isn’t worth the money saved.
As far as needs-based money goes, it is pretty rare. Loans are easily available for almost any school, and anyone can afford to go to law school on the loans. Sure, you have a lot to pay back, but unless you have a bunch of kids or have to support an elderly family member (which generally means you aren’t going to perform as well on the LSAT or on your undergrad GPA, so the issue is probably moot), you can afford to live during school, and after you will at some point make decent money, plus there are many repayment programs, etc. Harvard has a needs program, I think Columbia does, and a few of the top 30s also do, but they are mostly for small amounts.
Finally, the interview and the essay are not going to get you into a school. What they will do is keep you out of a school if you mess them up. There are some very rare cases where a well-written essay can explain away a bad facet of your app (I have a crappy GPA because I was battling cancer/drugs/religion/the internet). Most people don’t have a big split, because both GPA and LSAT correlate fairly well with academic ability, so if you’re dreaming of taking the LSAT and getting into Yale after you graduate with a 2.0 from DeVry, you’ll be disappointed. But if you have a fantastic LSAT and an average GPA (3.4-3.6), you will have good results, though it is unlikely you will get a full ride at the level of school you should be attending.