YES. I was looking at 40 gallon tanks the other day (at a different store) and they're normally about $150. Even on craigslist they usually go for $40 and up. Makes me wish I had a Petco near me...
If you think you're going to need more than one 40 gallon tank, then yeah, go for it. Just remember it's kind of a big thing to have sitting around if it's not being used.
I ended up buying the 40 gallon breeder and a 20 gallon long so final price was $65. But minus $5 for a coupon I had then another $15 I had from my pal rewards and another $2 from a survey I took final price. $43.75. SCOOOORE!!!!