Wiki for Advents Japanese sales.
Mega Man ZX Advent was the tenth best-selling game in Japan during its release week at 21,379 units sold.[22] 63,977 units of the game were sold in the region by the end of 2007.[23]
Mega Man Zero
Capcom reported healthy sales of Mega Man Zero during its release period.[37][38] It was the third best-selling video game in Japan during its week of release at 66,990 units.[39] Famitsu sales data supports that Mega Man Zero sold 135,850 units by June 2002 and 231,166 units by the end of that year in Japan alone.[40][41] The popularity of Mega Man Zero spawned three direct sequels on the GBA
Mega Man Zero 2
Mega Man Zero 2 was the seventh best-selling video game in Japan during its week of release at 53,839 copies and climbed to the number one spot the following week with an additional 25,283 copies sold.[16][17] The game appeared on Famitsu magazine's top 30 best-sellers list for the following four weeks.[18][19][20][21] By the end of 2003, Mega Man Zero 2 had sold 158,479 copies in Japan alone.
Mega Man Zero 3
Mega Man Zero 3 was the fourth best-selling video game in Japan during its week of release.[13] It was the 106th best-selling game in the country for 2004 at 121,847 units sold.[
Mega Man Zero 4
Mega Man Zero 4 entered Japanese sales charts at number eight during its release week.[31] According to Media Create sales information, Mega Man Zero 4 was the 177th best-selling video game in Japan in 2005 at approximately 74,354 copies
Mega Man Legends 2
The PlayStation version of Mega Man Legends 2 was the 139th best-selling video game in Japan in 2000 at 88,131 units sold.[58] The PSP version of the game barely made it into the Famitsu top 500 best-sellers list in Japan for 2005 at a mere 15,309 units sold by the end of the year.[59]
Also Capcoms own sales data released a few years ago.
Mega Man Series (120 titles, 28,000,000)
This logic basically applies to every game in the MM series, the initial game sells a lot, the next game sells ok, and it gets worse and worse, but after Zero the ZX series never really took off in a meaningful way, and while MM9 seemed to sell a lot, 10 was noted to be a lot less successful. It's as if people think Capcom was seeing big numbers and said man, fuck money, let's not make that anymore. There is a reason the series tapered off, and it wasn't a hate of fans and money.
Let's do a fun math game and be really generous with it too, let's just assume the amount of 'main' Mega Man releases is actually much less than 120. Lets say there have been 40 'main' releases of the MM series all around on portables and consoles, now lets say the units sold was actually 30 million, that would be around 750k sales per game. Unfortunately, there have been many more releases than that, and some of those games (Mega Man 2, 3, X) sold some millions of units. Does this really seem like a high selling and powerful series?
If any of my information or math are wrong, i'm happy to be corrected. I own almost every single US release of the Mega Man series (only missing 1 game boy and the game gear title) so please know, I love this series, and I hate what has happened to it. I just also can kind of see why Capcom has neglected it when the RE series outsells the entire MM series combined after 4 or 5 games -_- Also keep in mind, that Mega Man Powered Up and Maverick Hunter X were both meant to be the first of many, and this was way before Capcom abandoned the series, once again, it must be that they sold a lot and Capcom are just jerks, right?
With that said, I think i'll be putting in 60 for this particular game as I'd like a boxed 'release' for my collection, I fully support the idea of the game since obviously no one else is doing it, but I also understand that this option isn't really viable for big companies and also understand the difference between appealing to 100,000 people who are willing to put in money for a digital release, vs a company trying to make a big budget game that sells at a fixed price and needs more than 100k people to profit.