I agree with you

. What should be a good lumen choice on front lights, in order to make good balance about the performance and price? I see that more lumens also higher price.
That will depend on how much YOU want to spend. Personally, and I have done this, is to buy a really nice main light like the Raveman PR900 (meaning 900 lumens max) for around $75 on Amazon, or the PR 1200 for around $90 on Amazon. Those two lights are the best for the money as of 2019. Those used aimed optics as well, similar to a car headlight, so it has a cut off on the top portion of the beam as not to blind motorists as much, this was a feature that Phillips invented and had the first bicycle light made with that feature that I use to this day called the Philips Saferide 80. This video compares the Raveman PR1200 to the Philips Saferide 80, please watch this carefully:
https://www.bing.com/videos/search?...300EBA56A098B4ACA5C6300EBA56A098B4A&FORM=VIRE From this video I think the PR1200 is too much light unless you plan on doing off road gravel or single track riding, I think I would save the $250 and get the PR900 because even with my old 66 year old eyes my Saferide 80 is plenty bright for me, in fact most of the time I run it in low mode.
The Saferide 80 is no longer in production which is unfortunate, it was a very solidly built light made of thick aluminium, and it ran on 4 AA rechargeable batteries, this was good and bad, the good was that batteries could be bought at any store, and you could even use non rechargeable bats, the bad news was the runtime on rechargeable bats was about 6 hours on low and 2 on high, but that was plenty of time for me. Also what confused buyers was that it only put out 220 lumens according to the box, however being a cut off beam the beam looked like 900 to 1000 lumens, it was WAY brighter than my old Cygolite that put out 400 lumens.
Now here is the second thing I've done and it works really well, and that is to buy a small light with 400 or so lumens and attach it to your helmet, this way you can aim the light anywhere you want including into the window of a car trying to pull out in front of you. For this I got a Lezyne Mini Drive 400XL which costs just around $30, these are real small and lightweight and can be put on a helmet with the optional Universal LED Helmet Mount that cost $10. Run time is a bit short with the Mini due to size constraints, it will only burn for about a hour on 400 lumens but most of the time I run mine on strobe mode they call Day Flash which flashes at full power for as long as 7 hours, but in reality it's closer to 5 hours.
Not sure what you have done about your rear lighting but I also use 2 rear lights, I use a NightRider (NR) Omega 300 as my main light, that thing is intensely bright, that's 300 lumens! it cost around $55 which I think is a great deal considering the brightness of it. The other light I use is the NR Sentry Aero 260, this light has a really nice side lighting feature that is extremely attention attracting, but the 260 lumens is way overrated, it's probably closer to 150! but it does work good just not very good in the daytime like the Omega 300 can do. I also noticed that cobb LEDs, like those in the Sentry Aero 260, washes out in direct sunlight, something I wasn't expecting, so I only use that light now at night, that light costs $45. The only place you can buy the NR lights is on the NR website.
If money is short I would buy the brightest light first, then when you can afford it add the second dimmer light. I do seriously believe from seeing cyclist at night while either riding or motoring in my car that a cyclist with more than one headlight and or tail light attracts more attention then a single light and that's why I suggest buying two. I also suggest if you have or get two lights that you have the brightest one on steady and the other on strobe, this includes the tail lights too. The Sentry Aero 260 doesn't have a strobe function, it does have the ability to alternate between the rear facing light and the side facing lights which is pretty attention grabbing.
Anyway those are my suggestions, others will have other suggestions and that's fine, you'll have to do your own research and see what might work best for you.