I found a search tool in nightview.info.
https://www.nightview.info/yakei/There are 19 observatories in Osaka. This link shows all from the most beautiful.
https://www.nightview.info/search.php?keyword=&area_id=27&genre_id=5&p...[1]=&search_env[2]=&search_env[3]=&search_env[4]=&search_env[5]=&search_env[6]=&search_env[7]=&search_env[8]=&search_env[9]=&search_env[10]=&sort=2
Here is an extract of 16 observatories with more than three stars. The first column is the rank in beauty, the second is the number of stars in beauty, the third is the total cost in yen (entrance fee + public transportation either from Umeda or Namba), the fourth is the time in minutes needed to get there (either from Umeda or Namba), and the fifth is the link. The third and fourth columns assume an arrival by 19:00 on May 19 using Google maps.
1 5 1690 9
https://www.nightview.info/yakei/detail/abenoharukas/2 5 980 30
https://www.nightview.info/yakei/detail/wtc_osaka/3 5 180 4
https://www.nightview.info/yakei/detail/orixhonmachi/4 5 1000 12
https://www.nightview.info/yakei/detail/skybldg/5 4 470 29
https://www.nightview.info/yakei/detail/higasiosaka/6 4 260 25
https://www.nightview.info/yakei/detail/sakaicity/7 4 260 30
https://www.nightview.info/yakei/detail/takatsukicity/8 3 0 9
https://www.nightview.info/yakei/detail/hankyugrandbill/9 3 180 13
https://www.nightview.info/yakei/detail/keihancitymall/10 3 0 6
https://www.nightview.info/yakei/detail/gfo_south/11 3 0 8
https://www.nightview.info/yakei/detail/gfo_north/12 3 100 10
https://www.nightview.info/yakei/detail/osaka3bill/13 3 880 11
https://www.nightview.info/yakei/detail/tsutenkaku/14 3 190 12
https://www.nightview.info/yakei/detail/abenolucias/15 3 830 15
https://www.nightview.info/yakei/detail/osakamuseum/16 3 0 6
https://www.nightview.info/yakei/detail/kazenohiroba/One five stars (Orix), two four stars (Sakai and Takatsuki), and seven three stars (Grand, CityMall, GFO_S, GFO_N, 3bill, Lucias, and Kaze no Hiroba) are less than 300 yen.
For the Osaka Bay area, there are 19 entries.
https://www.nightview.info/search.php?keyword=&area_id=27&genre_id=3&p...[1]=&search_env[2]=&search_env[3]=&search_env[4]=&search_env[5]=&search_env[6]=&search_env[7]=&search_env[8]=&search_env[9]=&search_env[10]=&sort=2
Only five have more than three stars.
1 3 280 28
https://www.nightview.info/yakei/detail/tenpouzan/2 3 280 26
https://www.nightview.info/yakei/detail/seaside_cosmo/3 3 1270 65
https://www.nightview.info/yakei/detail/tajirisky_bridge/4 3 280 42
https://www.nightview.info/yakei/detail/namihaya_bridge/5 3 370 49
https://www.nightview.info/yakei/detail/konohana_bridge/Three three stars (Tempozan, Seaside Cosmo, and Namihaya) are less than 300 yen.
There is another list of the best 30 in Kansai.
https://www.nightview.info/best/kansai/I think the first two (beauty and atmosphere) of the four indicators should be the maximum (five stars). Only four satisfy this condition; Harukasu, Sky Building, Rokko Garden, and Maya. For a completeness, here is info for the last two in Hyogo prefecture (no entrance fee for the both). Maya is known to be one of the top three night views in Japan. I believe night views are usually better to see from a distance.
1 5 1500 85
https://www.nightview.info/yakei/detail/maya/2 5 1470 91
https://www.nightview.info/yakei/detail/rokkou_garden/http://koberope.jp/en/maya