I am suspicious of this fruit-altitude analogy due to its long history of use, and 100% failure rate.
It's definitely an exaggeration to say that all science on a shoestring budget has already been accomplished, there are new frontiers out there. But once they start gaining momentum, the low hanging fruit will be consumed in due course. Methodically searching a domain works and works from the most tractable end up until it is at the frontier of what is tractable given our current technology/constraints.
I don't really understand the alternative hypothesis. That there's an infinite amount of low hanging fruit? What's this 100% failure rate?
Perhaps this will help: Indeed high energy physics is a very high budget project! But there are many areas of the natural sciences which are not high energy physics. This area has been a big deal over the past few decades, and I wonder if it's an over-commitment at the expense of other areas.
You can do many molecular bio lab techniques with a budget of $10k in equipment and reagents, for example. (If used/entry level) I believe there are also many areas in science, chem, and bio which can be done on a theoretical level, or with computers, etc.
Another angle: We are in the earliest steps of neuroscience. Many biology tools and techniques are borrowing something serendipitous we found in nature (CRISPR, TAQ polymerase etc, leveraging living cells' equipment to produce proteins etc). We have no concept of a general chemistry simulator. Molecular dynamics simulations can only work on very small systems for very small timescales, and are based on many approximations, and assumptions which provincialize them. We are very likely missing a big picture of the lower levels of GR/QM. It is very hard for me to agree with "Yep we're good; nothing left to discover here without really expensive equipment!".
I would point out that that's on the back of a huge amount of research funded by grants and performed in national labs, but it doesn't impact your argument.
Higgs didn't use the LHC to write the paper which won him the Nobel prize.
Additionally, I think it's worth considering that the availability of the money that built the LHC alleviates the drive to find different solutions.
As they say, "necessity is the mother of invention." I frequently think of the great pyramids and people being baffled on how they would build something of that scale without modern equipment. It's hard to get your mind to come up with novel ideas when it already knows that you'd use cranes, trucks, etc. to do it today.