There are two types of mods: those I like and those that I don't.

As a maker of the Pinduino, I completely understand how people's tastes are different. Some people like over-the-top lighting effects and some don't, and I hear from people on both sides of that discussion (though it is just personal taste).

As the writer of several DIY guides:

https://pinside.com/pinball/forum/topic/diy-repair-20-10293-reed-switch
https://pinside.com/pinball/forum/topic/diy-guide-to-adding-backbox-lights-to-dialed-in
https://pinside.com/pinball/forum/topic/diy-cabinet-side-aka-stadium-lighting
https://pinside.com/pinball/forum/topic/how-to-make-an-led-backbox-for-30-for-modern-sterns

I write these up so people can make their games more to their liking. Not to knock any mod maker, but what is charged for some of them is a bit. . ridiculous (and some are worth every penny). However, I do know the time it takes to order and do quality checks on parts, put kits together and test them for people, do user support, etc. But if someone likes to make things and can put an hour or two into a project, they can save themselves a lot of money.

Still, do any of these mods increase the value of the game? For some mods, sure (one of my favorites is the mini Tron Arcade). For others, well, if you overpaid $100 for a Hallmark ornament I can find on EBay for $5, don't be insulted when other people aren't impressed.

I think people are tired of discussion on pinball prices. It comes up a lot (A LOT), and the answers are mostly the same:

1. Supply and demand
2. NIB games are more expensive than they were 5 years ago; makes low end games more expensive
3. Remakes make hard-to-find-and-desirable games less expensive
4. People ask high prices for games with lots of mods (people expect to get all their money out of a game for money spent on mods)
5. People expect that their time is worth something "restoring"/shopping a game, but they don't necessarily have the skills to do the job well (I don't expect that my time is worth anything working on a game as compared to the time HEP puts into a game. One hour of his time IS worth something to people in pinball; one hour of my time is not.)