Is it time to star re-manufacturing now expensive equipment such as flicker fixers, accelerators, CD interfaces and other interfaces for example?
It all depends on if the parts are available, custom parts like the Amiga connectors are expensive to be made, specially in small batches. This makes cheap A600 memory cards and other things to expensive to make even though the actual parts are cheap.
Flicker fixers for example look super simple stuff yet they easily fetch over £100.
The standard external flicker fixer design has a adc then about 2meg of fifo ram (I think the toasterscan uses four meg if its got a flicker fixer onboard or two otherwise) and then a cpld to control it all, followed by a dac.. its not as easy as it sounds and with each of those chips costing pounds, not pence the card would still end up around the £75 mark once product warrenty, a markup for the maker and a markup for the seller is taken into account.
You will find a lot of modern Amiga cards (past seven years) use one large FPGA/CPLD to do as much in one chip as it can. (The new Z3 USB card, Picasso IV and Prometheus cards are good examples) as they are good for short production runs and reduce the risk of major design problems needing rework. (you just reprogram the chip and send the card back out)
Also dont forget you need the product CE marked for EU sale, FCC marked for American sale and in the EU it must be Pb free and RoHs compatiable.. is your cheap China PCB supplier? Fines await if you just stick CE marks on or use lead coated components.
So lots to think about, an easier way is to do the design, upload it to Aminet for free and see people make them and flog them on eBay as individuals.