Don't let the nay-sayers put you off.
It's not exactly difficult to make - anyone who can't cut in a striaght line must be a bit of a biff. Yes, it does take time and cutting stainless steel is a right pain, but all you are doing is cutting squares with slots. Hardly difficult.
That said, £35 for a Honey Stove is an extremely good price. If they'd been around when I made mine, I would have been sorely tempted.
As for cost. Well, I got the stainless steel free (i went to a local sheet metal workers and asked for some. I was happy to pay for it, but when they saw how much I needed they gave me some offcuts for free!). You will get through a LOT of Dremel discs. Don't underestimate how many you will use. You will also need earplugs and a face mask. I would say mine cost me about £15 to make.
Yes, it took time. But you can't value you own labour at a cost. And anyway, making one yourself is its own reward.
A good idea is to make one in card first. I found the original Nimblewill plans slightly too small. I added about an inch in height and maybe 2 or 3 inches in width and depth. So, make one in card first, and see how big you want it. When you have the templates the size you want them transpose them to the metal and off you go.
It's INCREDIBLY easy to make. And satisfying. And much cheaper. But it is noisy, dirty and takes a while.
I'm glad I made my own. In truth, not sure I'd so it again (but then, I don't need to). But I would also recommend anyone to make one for themself rather than buy, but just make sure you get the dimensions right first time.