I bought my kid his first BMX (this 16" Sunday L'il Spark) for Christmas 2013 when he was 4yrs old.. it was his first bike.
..alas, he couldn't touch the floor (which i'd anticipated) so i had to attach stabilisers, being a proper sized down BMX they wouldn't fit so i found myself at work on Christmas morning, slightly hungover, machining the slot out on the Bridgeport
The stabilisers were a terrible idea, when he truned a corner it threw him off .. so it took him 13mths before he could touch the floor.. by March 2015 aged 5.5yrs, it was perfect.. he rode it everywhere.. at age 10, he grew out of it and moved onto a full size BMX
..i bought it before Brexit, before our economy turned to shit.. i think i paid £280 from Waller BMX in Sheffield.. he rode it for 5yrs and i sold it on eBay for £230 so he rode an amazing, bombproof, highend BMX for 5yrs and it only cost me £50.. i can't complain with those bike-onomics.