If you are a hobby EE (and works as a software engineer for your day job), $6 is negligible. Some of the higher end RF chips cost 3 figures per chip. Cost of BOM only truly matters at scale.
IE: I'm going to sell something for $150 to $500 in relatively small numbers, that meaningfully helps people with some specialized niche task that big companies are blind to... with a BoM aimed at maybe $30 and an overall production line of 1-hour (assembly time + testing / manufacturing / boxing) time or less, since I'd likely be the only person boxing these devices up and shipping them out.
I mean, ideally maybe like 10-minutes assembly time or shorter really. Depends on how much time you're valuing your labor.
I bought an HDMI lag tester that proved whether monitors for the fighting-game community were 18ms lag or 30ms lag, since the fighting game community is very, very, very particular about tournament setups. There's no way a device like this would make a sale at the large scale, but that's the kind of "Etsy-project" that I literally bought back when I cared a lot of about getting my home setup close to tournament specs.
Or perhaps $300 joysticks custom built to look/feel like arcade sticks, at least before Madcatz / big guys started making them.
In case you're curious: this was a $120 doohicky that was an HDMI output signal that flashed white-rectangles on the top-left, top-right, center, bottom-left, and bottom-right of the screen, .... plus a photodiode that accurately measured when the HDMI-signal went out minus the latency to the milisecond. The last time detected was updated through HDMI output.
This is a project most of us hobby EEs could accomplish and likely sell on Etsy. But we gotta keep costs down below $30 BoM in practice. Its a meaningful project and something good tournament organizers knew to buy and test with.
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I've heard the estimate that for hobby / Etsy store level manufacturing, you're looking at 5x BoM for a fair price. Ex: $20 BoM sells at $100, $100BoM sells at $500. If you can't accomplish this, then your business idea sucks, go think of another more profitable idea. If this niche product exists, then you've got a potential Etsy-business idea.
I think there's a good market for $100 to $500 specialist niche electronic tools like this, taking advantage of the small sizes of communities, small scale of builds, small markets, etc. etc. (If it were a large market, Hasbro or Nintendo or some "big guy" will jump in and likely take your market. If its like 1000 total lifetime sales, that's enough to make the hobby worth it but small enough that no big company would tackle that niche).
If you're talking about $500 parts, then we're talking about $2500 sales price (using the 5x BoM fair price scaling as a mental model), which is likely outside of the hobby/Etsy craft tool for niche subject market.
There's a lot of hobbies out there where $100 to $500 tools (ex: $100 HDMI lag tester, $300 joystick, Replicated Pop'n Music controller), is fair. Going above $500 or $1000 Bill-of-Materials (aka: sales prices in $2500+ range) kind of gets you back into professional tools and you're suddenly a loser.
iCE40 is a $6 surface mount chip, which means I'm comparing it against all other $1 to $20 chips within my capability to put into OSHPark's 6-layer PCB-layout service.
My toolbox includes 8-bit uCs like AVR (ATMega, AVR DD, AVR EA), 16-bits like MSP430, 32-bits like Cortex-M0+, M4, M7. It includes Linux-scale Microprocessors like Microchip SAMA5D2, Microchip SAM9x60-D1G, or Boards like Beaglebone or Rasp. Pi. (And yes, I've double-checked. These 0.80mm pitch BGAs seem like they fit and route on OSHPark's 6layer 5mil trace/space impedance controlled specifications)
So where does an FPGA fit inside of here?
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Strangely enough, "Glue Logic" is an 8-bit territory these days. AVR DD has CCL, which are a 4x 3-input LUTs + 2x JK Flipflops + Event system that executes even while the 8-bit CPU is asleep.
See here: https://ww1.microchip.com/downloads/en/AppNotes/TB3218-Getti...
So the smallest "glue logic" purposes of FPGAs is... well... outcompeted. The $1 uCs are beating FPGAs at this particular task now. I truly can configure 12 input pins of the 8-bit uCs + 4-output pins to act as simple glue-logic fully async from the uC's clock (IE: zero code / MHz used, still functional during sleep, etc. etc. Bonus points, Event-routing system means that events route to the ADC/Timers/etc. etc. even while uC is sleeping, for maximum power efficiency). If some latency can be tolerated, you can even hook up these CCL / routing to interrupts and run a bit of code on it.
AVR DD's CCL isn't good enough for any serious design like a 32-bit LSFR. But you know, a CRC32 (LSFR implementation) probably would be best done on such an iCE40 FPGA rather than the 8-bitter's piss-poor compute capabilities. But 3x AND gates + 1x XOR gate scattered across the board? That's an 8-bitter job today.
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I think the answer for "What is the best total solution under $50" will likely be microprocessors and full scale chips. (Or even a full sized SBC like Rasp. Pi or Beaglebone).
But if we change the question to "What is the best total solution under 50mA", suddenly the FPGA is far more competitive. FPGAs aren't that expensive, now that I'm looking up these tiny iCE40 chips. But 1k LUTs is still pretty small.
Speaking of which: ouch. A lot of iCE40 are 0.40mm and 0.50mm pitch BGAs, so no OSHPark 6-layer for those. QFN and TQFP are available though. So just be careful about chip selection and think about the PCB you're planning to use with these chips.