greenhouse Are any of these greenhouses that are on sale worth getting?

Once again I was on one of my favorite sites called woot, this week they are selling portable greenhouses for what appears to be a good price.  Are they worth getting at this price, or would it be better/more cost effective if I were to make my own?  I have no experience whatsoever with greenhouses, the closest thing I've used is my indoor grow/OW setup.  One or two of these appear to be a decent size, but I'm having a hard time visualizing how many plants they could hold...
Those are comparable to the kind they sell at tractor supply. I have a 4 shelf one I got at
Tractor supply I got this spring and i really like it. I just bought an 8 shelf walk in from tractor Supply on sale about A month ago. Price wise the ones at tractor supply are alittle cheaper.
I cannot pull up the link. I've built 5 greenhouses in the past ten years. Now granted I'm building larger than portables. And I've been tweaking as I upgrade. I only have one greenhouse now as it is st a new place and I'm actually working on the fifth.

The thing with the kits I've found is the size is smaller and materials not as strong as you could make yourself. Now with that said I wasn't able to go to the link and see what you were looking at.

For instance. Harbor freight sells greenhouses. They seem to be a decent price. They need modification for them to last. The metal needs reinforcing and the door tweaked because it doesn't seal. And for the money, even at harbor freights prices, I've found I could build a larger greenhouse for about the same.

About 8 years ago atlas was selling a 48" hoop house with heater and vent fans for about 5-6k. That's a too price I think but you still had to build your own front and back wall. And its a huge greenhouse.

Now with all that said. IDK your building skill level in that case you would be better off buying a kit house. And there are several things to remember about greenhouses. You have to known how you are cooling it. Because even in winter they can get hot in the sun. Just likens car sealed up in a parking lot. They get hot inside. Air movement is a must inside the GH to prevent mold and other illness. Heating in the winter. How do you plan to do it. Propane is the best bang for your buck but heaters are pricey. Electric goes out if you have a power outage. Nat gas is good too. Just not as high a bang for buck as LP. Nat gas and LP heaters can be pricey up front. Then also have to think do you need a wet wall or also known as swamp cooler in the summer to help aid in cooling. Then are you going to be there daily to open it up or do you want it automated to open vents and turn on fans? Do you want misters to aid in cooling and humidity or use the wet wall to do that?

Being on the pepper forum I assume its for veggies and peppers and not something specialized like orchids or Nepenthes. So that makes it easier because you don't have really a max temp that isn't easily obtainable through a wet wall and fans.

How big would you like the GH to be? In my experience I can easily fill a 12'x16" greenhouse in no time and that is with orchids and Nepenthes. That's not with peppers and other plants that get bigger quicker.

If you are located where it get cold cold in winter are you going to heat or only use when its not too cold? Year round growing or just to start a season early?

There are many questions you need to ask yourself before committing to a greenhouse. They are not cheap even when building yourself. They take upkeep and maintenance. And then how nice would you like it? If you are just going for functional there are several plans for PVC framed GHs that are nice. But if you want to go with esthetics as well as functionality then it will cost a little more.
Some have had some success with those I have not you may want to rebuild the structure with wood or pvc maybe add chicken wire if you want it out year round.
i like the PVC DIY hoophouses (search youtube) they are pretty cheap.
I have one of those small portable greenhouses its like 4ft high 2ft wide it's ok i guess but it doesn't really keep that warm in a freeze.. 
I use the 5 tier for my mushroom growing but don't see it being useful for pepper growing other then starting seeds etc..
For the money. PVC or even treated 2x4's are better and cover with 6 mil clear plastic from lowes. It lasts a season and existed out to about the same price as greenhouse plastic but has to be recovered yearly in full sun applications. Greehlnouse glazings are expencivem