Honestly i have spent hours looking in the past and I never see what I consider to be good priced decent skeletons this time of year. Costco generally has the best deals starting in July or August for around $40 each.
The other good time is in stores like Walgreens when they put their left over skeletons on sale after Halloween and you can pick them up for $12 each if you hit the right store at the right time.
In a pinch I have been known to take a cheap bluckie and modify it, replace the skull with a better looking skull and shadow the ribs and do things like that to make it work as a "creepy" skeleton. This would be my budgetary approach in a sudden situation, as really decent plastic skeletons tend to be a little pricey.
I have 24 pose and stay skeletons in our inventory. The first one my wife got years ago from Grandin Road for $90. And we once had several bucky ones that have mostly been replaced now, but I have managed to take a couple of those and using 1/2" PVC to redo them and make them a little more sturdy. There is a video someone posted on how to make them posable with PVC if you are looking for a very inexpensive solution. As for the Pose and stay we have picked them up for as little as $30 up to $90. most of them came from Menards for $30 or target for $40. All with great quality.
Other than hitting an after Halloween sale at the right store at the right time, the best regular price deal I've been able to find on a full size skeleton with "descent" quality is $30 from Home Depot. The quality is not great (but descent) and its clearly a seasonal item, but that's the best bang for the buck I've found so far.
I agree with 65Ace. Home Depot has a great price on skeletons for the Halloween season. The quality is good for the price (its only a Halloween prop for cryin' out loud) and I buy 2 or three every year. If they are out of stock in their store I get them online for $29.99 including shipping.