What is the difference of 125khz, 13.56mhz and UHF ?

RFID is a benefit for access control, RFID jewelry tracking, identification, RFID retail inventory management application.
Passive RFID including 125khz/134.2khz low frequency, 13.56mhz high frequency, and 860-960Mhz (Regionally dependent) UHF.
What ‘s the read range difference between them?
First, RFID read range
In the late 1990’s the RFID industry began to gravitate toward 125 KHz as a standard. Most RFID systems today are based on 125 KHz.EM4200 is 125khz low frequency, and the TK4100 is compatible EM4200 but cheaper than it.
The read distance of EM4200 ISO Card is up to 50cm, but the EM4200 RFID tag will be shorter than EM4200 ISO card, as it is smaller.
134.2khz is low frequency too, the regular products are EM4305 PIT glass tag and EM4305 ear tag and RFID animal reader.
134.2Khz usually use for animal tracking, the read distance of PIT tag or RFID animal tag up to 7cm (transponder and antenna dependant)

The read range of 13.56mhz RFID reader and 13.56mhz RFID card is Between 5cm and 8cm (transponder and antenna dependant)
NXP Mifare classic 1k is 13.56mhz high frequency, this series including Mifare ultralight, Mifare 4k, Mifare DESFire ev1, and Mifare DESFire ev2, Mifare plus, etc.
They are the same read distance, but with different memory and security level.
NFC tag is 13.56mhz too, it including NTAG213, NTAG215, NTAG216, etc. They are short read distance.
NXP I CODE Sli tag/card is the longest read distance among 13.56 MHz, the read distance up to 15cm.

The 860-960Mhz UHF RFID reader and the long range RFID tags are up to 25 meters. (Transponder and antenna dependent)

The different frequency with complying with different ISO standard.
The 125khz low frequency complies with ISO 18000-2, the 134.5khz comply with ISO 11784, ISO 11785.
13.56mhz NXP Mifare series card /tag /reader comply with ISO14443A,I CODE SLI card /tag /reader comply with ISO15693.
860-960MHZ UHF long read range reader and tag are complying with ISO 18000-6C.

As the low-frequency 125khz tag is with slow data transmission rate, most user update their RFID system to 13.56mhz, it with Higher data read rate than LF tags.
But the UHF with Fast data transmission rate and excellent multiple reads capability. The LF tags and HF tags are only single read.

Which one is cheapest?
125khz LF card is expensive, besides the TK4100 card.
13.56Mhz card depending on the type of RFID chip, the Mifare 1k is the cheapest one among 13.56mhz.
UHF tag has a big demand in the market, so the price is very cheap.
The RFID reader should match the RFID card or RFID tag. They are should be the same ISO standard, same frequency, and the same RFID chip.
The 125khz RFID tag is read-only, so the 125khz RFID reader only can read UID, it ideal for reading unique items at short range.
13.56mhz RFID card support read and write, user can read and write card by 13.56MHZ RFID reader-writer.
UHF with longer read distance than LF or HF, Excellent performance in environments with high tag density.