Looking at amazon these are the cheapest
https://www.amazon.co.uk/LAOLIU-Automatically-Adjustment-Functions-Disassembly/dp/B08TBDWYK3/ref=sr_1_22?crid=32M4VR9Q28V1T&dchild=1&keywords=adjustable+dumbbells+sets+50kg&qid=1611599130&sprefix=dunbell+adju%2Caps%2C176&sr=8-22

https://www.amazon.co.uk/ZHENG-Adjustable-Automatically-Adjustment-Intelligent/dp/B08SGF3P77/ref=sr_1_32?crid=32M4VR9Q28V1T&dchild=1&keywords=adjustable+dumbbells+sets+50kg&qid=1611599130&sprefix=dunbell+adju%2Caps%2C176&sr=8-32

if you want cheaper you will have to get more traditional ones like these

https://www.amazon.co.uk/Phoenix-Fitness-Dumbbells-Strength-Training/dp/B08MWDKSWJ/ref=sr_1_6?dchild=1&keywords=dumbells&qid=1611599262&sr=8-6

the ones on ebay are cheaper but its ebay

https://www.ebay.co.uk/itm/24kg-adjustable-dumbells-set-brand-new-RED/313383501618?hash=item48f71cbf32:g:4~4AAOSwjqFf~hUY

This one has a sale and is cheaper for a limited amount of time
https://www.powerhouse-fitness.co.uk/bodymax-25kg-selectabell-10-in-1-single-dumbbell-v2.0-wtfd2156

https://www.gsalunkhe.com/index.php?main_page=product_info&products_id=718571

£ 199 on eBay site and on this link

https://bit.ly/3sUBzGU

https://www.amazon.com/-/es/Bodymax-Selectabell-Juego-mancuernas-Negro/dp/B000XJ9VKS

https://www.walmart.com/ip/ATIVAFIT-Adjustable-Dumbbell-27-5-55-71-5-Pounds-Fitness-Dial-Dumbbell-with-Handle-and-Weight-Plate-for-Home-Gym-1-PCS/332639571?irgwc=1&sourceid=imp_V7zRWs19sxyLWeJwUx0Mo3EJUkERlG2RGURL0s0&veh=aff&wmlspartner=imp_10078&clickid=V7zRWs19sxyLWeJwUx0Mo3EJUkERlG2RGURL0s0&sharedid=verywellfit.com&affiliates_ad_id=612734&campaign_id=9383 Tis is best for you what you can get . the quality and is very good i hawe this one in im happy . mabey are beter but this is good prize and good quality cheer hope you like this one:D

https://shopee.ph/Adjustable-Dumbbell-24kg-52-8lb-with-15-increments-from-2-5-24kg-i.262200410.4543379938?gclid=Cj0KCQiAmL-ABhDFARIsAKywVacTzurSHDxX_TY1ZSyuhYIKDj3drx4SrEX_tfKcuTourmm7-qKJ4YQaAgYjEALw_wcB

Cheapest I can find only 60-70 Euro, 24 kg max weight Low delivery fee

Yes this is good

https://bit.ly/3sUBzGU 199 Euro e bay

https://www.amazon.com/4ActiveU-Adjustable-Dumbbell-Workout-Selectorized/dp/B08DKXV1Y3/ref=mp_s_a_1_14?dchild=1&keywords=Adjustable+Dumbbells&qid=1615594326&sr=8-14