so you mined same ammoun of BTC that you could buy at that time yes ? congratz
if not than i can understand before u didnt know it will not mine same ammount of BTC that you could buy at that time, but now if someone know it and buying device that will never make same ammount of BTC that it cost than that decision is just stupid ;p
simple example:
100$ for device that will mine 1BTC
1BTC=50$
ater some time prce going up
1BTC=300$
you paid 100$ for 2BTC before so you could have now 600$
but you have only 1BTC becouse your device cant mine anymore bcouse of difficulty .. its like 0.0001 per month now so thats mean you have 300$ and you are happy that you lost another 300 ;(
if going down
1BTC = 10$
if you bought BTC you have 2BTC thats mean you have 20$ so u lost 80$
if you bought device you have only 1BTC so it means you have 10$ = you lost 90$
conlcusion: its always better to buy BTC than overpriced bitcoin mining device that will naver mine same ammout of BTC that you colud buy at that time