Near the end of a developmental cycle studios usually pick up a lot of temporary people to help finish up. After the project is finished they just let them go. Since they should have made a profit(Or at least supposedly) this is really all I can think that it is. Though 40 employees sounds kind of high....
Sources: http://www.industrygamers.com/news/red-dead-redemption-needs-to-sell-4-million-copies-to-break-even-says-analyst/Source 1
http://www.digitaltrends.com/gaming/red-dead-redemption-ships-5-million-copies/ Source 2
Sig thanks to Saber! :D