Is $4,500 to replace a natural gas pool heater a fair price?

I have a fairly large 80,000L (20-22k gallons) salt water pool. My current 266k BTU natural gas heater, a Raypak series, only lasted 7 years before rusting out and failing, which is disappointing. Natural gas is very expensive here in Ontario, Canada, costing me about $500 extra per year to run the pool heater. My wife is keen on a heat pump, but the recommended 140,000 BTU model is quite expensive. I'm exploring alternatives because of the high cost and short lifespan of my previous gas heater. I'm interested in solar pool heaters as I have a huge south-facing roof (600-800 sqft) with plenty of sun. My idea is to combine a smaller 110,000 BTU heat pump with DIY solar heaters to compensate, but I'm unsure if this is a good approach. I'm also concerned about the durability of DIY solar kits and the overall lifespan of any new system, especially since my roof might only have 10 years left. I typically only use the pool from late May to mid-September. I'm trying to decide if it's worth spending $13,000+ on a heat pump if it will last 15-20 years and be cheaper to run than natural gas, or if I should just replace the gas heater for $5,000 despite my reservations.