Money talks bullshit walks.
But if you really care food has to be analyzed as you intend it to be eaten, freshness, cooking time and temperature, dressings, etc...since those will effect nutrients content.
Once done you are left with little that can be changed and no assurance whatsoever that your next buy at the grocery store for the same foods would yield the same results.
In order to mean something you should repeat the process many many times to get an average...yet in practical terms you'll be left with very little (not just talking about your bank account).
Once established the average folate content of your lettuce what are you going to do, compare it with the RDA in order to adjust you intake accordingly?
And whom tells you the actual RDA is really optimal and optimal for you specifically?
Luckily enough life doesn't need to be so complicate, commonsense and a tiny bit of knowledge are all you really need.
The worry of all the above will very likely be by far more deleterious to your health than a tiny discrepancy of folate consumption with what the RDA suggests.
If you are talking about pollutants, neurotoxics, endocrinodisruptors, carcinogenics and the whole lot well...it would be quite interesting indeed and according to the results some actions could be taken (change the brand, change the grocery store, decide to grow your own, etc...).