I found a way to get old sale prices that aren't in effect anymore.
Check out the $45 price of Sigma L in this link:
http://tfsource.com/fansproject/sigmal/
That pricing is from a sale that happened over 2 weeks ago. Now check out the updated price in this link for $70:
https://www.tfsource.com/fansproject/sigmal/
One of the links has the www at the beginning and the other doesn't, for some reason it's loading an old version of the site with old sale pricing that doesn't exist any more. I already tried adding the cheaper figure to my cart and checking out, it allows you to proceed right to payment and check out.
There are probably a number of other sales available with this method already as well. I would email them and let them know but I've emailed them many, many, many times in the past and they've never replied so I can only assume they don't care about anything I have to say.