The title question isn't really answerable. But there are certainly other sources which bear on that estimate. I'm going to gloss over the different estimates here for a moment. The article claimed the W&L estimate was $55M, one of the authors (I'll quote below) claimed $59M, and I've heard $43M and $53M in reference to this article... let's just say "approximately $50M".
To start with the obvious one, the study was primarily a counter to DiMassi's study that concluded the cost was around $800M per drug (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.128.4362&rep=rep1&type=pdf). There are some important considerations to make on this study. Roughly half of this $800M was "cost of capital" associated with keeping the pipeline open for an average of 96months/8years (the average length of time it takes to get a drug through clinical trials). For those of us who don't work with millions of dollars spent over decades, I don't think it's unfair to characterize the cost in the DiMassi study as $400million. Another criticism of the DiMassi study is that the source data was somewhat opaque. A third criticism (made in the L&W paper) is that the companies take excessive tax credits on R&D, and that drives their real costs down from what DiMassi claims.
Although I feel the $800M figure may be overstating things a bit, this newer study also has some severe problems. The most obvious issue is the cost of a phase III trial. Phase III trials usually have between 1,000 and 3,000 subjects, with an average cost of $26,000 per patient(“Clinical Operations: Accelerating Trials, Allocating Resources and Measuring Performance”, 2006). If you assumed no Phase III trial ever failed, that would still almost eat up the entire W&L cost estimate, just for a a phase III trial of 2,000 patients. Given that the failure rate is approximately 50% (http://www.nature.com/nrd/journal/v10/n2/full/nrd3375.html), I don't see how the ~$50M figure is defensible. You still have to accommodate the costs of pre-clinical development, Phase I and II trials and manufacturing development.
Some additional problems with the estimates come out when the original authors were questioned on it. Rebecca Warburton said in the comments section of that slate article (http://www.slate.com/id/2287227/pagenum/2#add-comment)
Our estimate of $59 million is the
median development (the “D” in R&D)
cost per average drug, not just NMEs
(new chemicals) and does not include
basic research costs, for which there
is no reasonable estimate available.
This is in spite of the fact that they referred to "R&D" throughout the paper, and actually did factor in 'basic research' costs to their estimate, while claiming that companies hardly do any. (I'll deal with that at the end).
Rebecca also claims that they did take failed drugs into account.
The discussions with the authors attached to that article are worth reading. Donald Light seems to be saying that he took DiMassi's estimate, and then subtracted everything he thought was unreasonable... rather than approaching the task at hand and estimating costs/discounts/etc.
For a direct confrontation between DiMassi and Donald Light, you can visit the abstract comment section of the L&W paper http://content.healthaffairs.org/content/25/2/461.abstract/reply . One important point to make (from that comment section) is that the R&D costs of a particular drug have no particular bearing on its price. Drug development is a sunk cost, after it is developed, the people who are buying it are paying for the development of the next generation of drugs. This is not a complex idea, and one that both DiMassi and Light understand (although there appears to have been a bit of a vocabulary misunderstanding early on)
The claim was made both in the L&W paper and in the comments section of this question that "most drug discovery is not done by companies". There actually is some data out there in the form of this study: http://www.nature.com/nrd/journal/v9/n11/abs/nrd3251.html . The sources of NMEs that eventually become drugs are:
- 58% from pharmaceutical companies. (big pharma)
- 18% from biotech companies.. (startups, VC-funded ventures)
- 16% from universities, transferred to biotech.
- 8% from universities, transferred to pharma.
The paper is quite worth reading for other breakdowns (universities are responsible for starting roughly 1/3rd of the 'innovative' drugs that make it to market, which is a significant increase).
TLDR: The $55M estimate is almost certainly too low. But the previous estimate of $800M is almost certainly too high. Nobody has the data we would like to have on this topic.
(Note that my lack of rep here forbids me from using too many links, a somewhat ridiculous problem on a site that could basically be named "citationneeded.com")